Essential University Physics, 3e (Wolfson) Chapter 5 Using Newton's Laws
5 . 1 Conc e p t ua lQue s t i o ns 1) A stalled car is being pushed up a hill at constant velocity by three people. p eople. The net force on the car is A) zero. B) up the hill and equal to the weight of the car. C) down the hill and equal equa l to the weight of the car. D) up the hill and greater than the weight of the car. ) down the hill and greater than the weight of the car. Answer! A "ar! 1
#) A bo$ of %ass m is pulled with a constant acceleration a along a horizontal frictionless floor by a wire that %a&es an angle of 1'( above the horizontal. f T is is the tension in this wire* then A) T = ma. B) T > ma. C) T < ma. ma. Answer! B "ar! 1
1 Copyright + #,1- earson ducation* nc.
/) Two Two weights are connected by a %assless wire and pulled upward with a constant co nstant speed of 1.', %0s by a vertical pull P pull P . The tension in the wire is T see see figure). 2hich one of the following relationships between T and P and P %ust %ust be true3
A) T 4 P 4 P B) T 5 P 5 P C) P C) P 6 6 T = 1#' 7 D) P D) P 5 5 T 6 #' 7 ) P ) P 5 5 T 6 6 1,, 7 Answer! D "ar! 1
# Copyright + #,1- earson ducation* nc.
/) Two Two weights are connected by a %assless wire and pulled upward with a constant co nstant speed of 1.', %0s by a vertical pull P pull P . The tension in the wire is T see see figure). 2hich one of the following relationships between T and P and P %ust %ust be true3
A) T 4 P 4 P B) T 5 P 5 P C) P C) P 6 6 T = 1#' 7 D) P D) P 5 5 T 6 #' 7 ) P ) P 5 5 T 6 6 1,, 7 Answer! D "ar! 1
# Copyright + #,1- earson ducation* nc.
8) Two ob9ects having %asses m1 and m# are connected to each other as shown in the figure and are released fro% rest. There is no friction on the table surface o r in the pulley. The %asses of the pulley and the string connecting the ob9ects are co%pletely negligible. 2hat %ust be true about the tension T in in the string 9ust after the ob9ects are released3
A) T 5 5 m# g B) T 4 4 m# g C) T : : m# g D) T 5 5 m1 g ) T 4 4 m1 g Answer! C "ar! 1
') Two bodies P bodies P and and Q on a s%ooth horizontal surface are connected by a light cord. The %ass of P is is greater than that of Q. A hori horizo zont ntal al forc forcee
of of %agni %agnitu tude de F F ) is applied to Q as shown in the
figure* accelerating the bodies to the right. The %agnitude of the force e$erted by the connecting cord on body P body P will will be
A) zero. B) less than F than F but but not zero. C) equal to F to F . D) greater than F than F . Answer! B "ar! 1
/ Copyright + #,1- earson ducation* nc.
-) Two unequal %asses M and m M 4 m) are connected by a light cord passing over a pulley of negligible %ass* as shown in the figure. 2hen released* the syste% accelerates. ;riction is negligible. 2hich figure below gives the correct free
A)
B)
8 Copyright + #,1- earson ducation* nc.
C)
D)
Answer! C "ar! 1
=) Two ob9ects have %asses m and 'm* respectively. They both are placed side by side on a frictionless inclined plane and allowed to slide down fro% rest. A) t ta&es the lighter ob9ect ' ti%es longer to reach the botto% of the incline than the heavier ob9ect. B) t ta&es the lighter ob9ect 1, ti%es longer to reach the botto% of the incline than the heavier ob9ect. C) t ta&es the heavier ob9ect ' ti%es longer to reach the botto% of the incline than the lighter ob9ect. D) t ta&es the heavier ob9ect 1, ti%es longer to reach the botto% of the incline than the lighter ob9ect. ) The two ob9ects reach the botto% of the incline at the sa%e ti%e. Answer! "ar! 1
' Copyright + #,1- earson ducation* nc.
>) A crate is sliding down an inclined ra%p at a constant speed of ,.'' %0s. The vector su% of all the forces acting on this crate %ust point down the ra%p. A) True B) ;alse Answer! B "ar! 1
?) A bric& is resting on a rough incline as shown in the figure. The friction force acting on the bric&* along the incline* is
A) zero. B) equal to the weight of the bric&. C) greater than the weight of the bric&. D) less than the weight of the bric&. Answer! D "ar! 1
1,) A wo%an is straining to lift a large crate* without success because it is too heavy. 2e denote the forces on the crate as follows! P is the upward force the wo%an e$erts on the crate* C is the vertical contact force e$erted on the crate by the floor* and W is the weight of the crate. @ow are the %agnitudes of these forces related while the wo%an is trying unsuccessfully to lift the crate3 A) P + C = W B) P + C : W C) P + C 4 W D) P = C Answer! A "ar! 1
11) f you swing a buc&et of water fast enough in a vertical circle* at the highest point the water does not spill out because an outward force balances the pull of gravity on the water. A) True B) ;alse Answer! B "ar! 1
Copyright + #,1- earson ducation* nc.
1#) A string is attached to the rear
1/) uppose a highway curve is properly ban&ed to eli%inate friction for a speed of 8' %ph. f your tires were bald and you wanted to avoid sliding on the road* you would have to drive A) so%ewhat below 8' %ph. B) so%ewhat above 8' %ph. C) at e$actly 8' %ph. Answer! C "ar! 1
18) 2hen a parachutist 9u%ps fro% an airplane* he eventually reaches a constant speed* called the ter%inal speed. nce he has reached ter%inal speed A) his acceleration is equal to g . B) the force of air drag on hi% is equal to zero. C) the force of air drag on hi% is equal to g . D) his speed is equal to g . ) the force of air drag on hi% is equal to his weight. Answer! "ar! 1
1') uppose the force of the air drag on an ob9ect is proportional to the speed of the ob9ect and in the direction opposite the ob9ects velocity. f you throw an ob9ect upward* the %agnitude of its acceleration is greatest A) right after the ob9ect is released. B) at the top of its tra9ectory. C) The acceleration of the ob9ect is the sa%e throughout the entire tra9ectory. Answer! A "ar! 1
= Copyright + #,1- earson ducation* nc.
5 . 2 Pr o bl e ms 1) The following four forces act on a 8.,, &g ob9ect! 1 5 /,, 7 east # 5 =,, 7 north / 5 ',, 7 west 8 5 -,, 7 south 2hat is the acceleration of the ob9ect3 A) ##8 7 in a direction -/.8( north of west B) /,, 7 in a direction -/.8( north of west C) /,, 7 in a direction #-.-( north of west D) ##8 7 in a direction #-.-( north of west ) #1,, 7 in a direction #-.-( north of west Answer! D "ar! 1
#) Two ob9ects are connected by a very light fle$ible string as shown in the figure* where M 5 ,.-, &g and m 5 ,.8, &g. ou can ignore friction and the %ass of the pulley.
a) Draw free
> Copyright + #,1- earson ducation* nc.
/) The figure shows a 1,,<&g bloc& being released fro% rest fro% a height of 1., %. t then ta&es it ,.?, s to reach the floor. 2hat is the %ass m of the other bloc&3 The pulley has no appreciable %ass or friction.
A) -, &g B) '8 &g C) 8> &g D) 8# &g Answer! A "ar! 1
8) A wooden bloc& A of %ass 8., &g slides on a frictionless table when pulled using a %assless string and pulley array by a hanging bo$ B of %ass '., &g* as shown in the figure. 2hat is the acceleration of bloc& A as it slides on the frictionless table3 Hint: Thin& carefully about the acceleration constraint.
A) 8.1 %0s# B) /.' %0s# C) /.1 %0s# D) #.= %0s# Answer! A "ar! 1 ? Copyright + #,1- earson ducation* nc.
') The figure shows two 1., &g
A) 1> 7 B) 1' 7 C) #.? 7 D) /.' 7 Answer! A "ar! 1
-) Three ob9ects are connected by %assless wires over a %assless frictionless pulley as shown in the figure. The tension in the wire connecting the 1,.,<&g and 1'.,<&g ob9ects is %easured to be 1// 7. 2hat is the %ass M 3
A) >.// &g B) //.? &g C) /'., &g D) '#.> &g ) ?'., &g Answer! D "ar! 1
=) Three ob9ects are connected by %assless wires over a %assless frictionless pulley as shown in 1, Copyright + #,1- earson ducation* nc.
the figure. The tension in the wire connecting the 1,.,<&g and 1'.,<&g ob9ects is %easured to be 1// 7. 2hat is the tension in wire A3
A) >=.' 7 B) #8' 7 C) #>, 7 D) /// 7 ) '1= 7 Answer! D "ar! 1
>) A #,.,<7 bo$ rests on a ',.,<7 bo$ on a perfectly s%ooth horizontal floor. 2hen a horizontal 1'.,<7 pull to the right is e$erted on the lower bo$ see figure)* both bo$es %ove together. ;ind the %agnitude and direction of the net e$ternal force on the upper bo$.
Answer! 8.#? 7 to the right "ar! 1
?) A bloc& is given a very brief push up a #,.,( frictionless incline to give it an initial speed of 1#., %0s. a) @ow far along the surface of the plane does the bloc& slide before co%ing to rest3 b) @ow %uch ti%e does it ta&e to return to its starting position3 Answer! a) #1.' % b) =.1- s "ar! 1
1,) A child on a sled starts fro% rest at the top of a 1'( slope. f the trip to the botto% ta&es 11 Copyright + #,1- earson ducation* nc.
how long is the slope3 Assu%e that frictional forces %ay be neglected. A) #?/ % B) '>- % C) 11/, % D) 18= % Answer! A "ar! ',6
11) A syste% co%prising bloc&s* a light frictionless pulley* a frictionless incline* and connecting ropes is shown in the figure. The ?.,<&g bloc& accelerates downward when the syste% is released fro% rest. The tension in the rope connecting the -.,<&g bloc& and the 8.,<&g bloc& is closest to
A) /, 7. B) // 7. C) /- 7. D) /? 7. ) 8# 7. Answer! "ar! 1
1#) A ',.,<&g bo$ rests on a horizontal surface. The coefficient of static friction between the bo$ and the surface is ,./,, and the coefficient of &inetic friction is ,.#,,. 2hat is the friction force on the bo$ if a) a horizontal 18,<7 push is applied to it3 b) a horizontal 1='<7 push is applied to it3 Answer! a) 18, 7 b) ?>., 7 "ar! 1
1# Copyright + #,1- earson ducation* nc.
1/) A 8.,,<&g bloc& rests between the floor and a /.,,<&g bloc& as shown in the figure. The /.,,<&g bloc& is tied to a wall by a horizontal rope. f the coefficient of static friction is ,.>,, between each pair of surfaces in contact* what horizontal force F %ust be applied to the 8.,,<&g bloc& to %a&e it %ove3
A) 1-.# 7 B) '8.? 7 C) #1.1 7 D) #/.' 7 ) =>.8 7 Answer! "ar! 1
18) A 1',<7 bo$ is being pulled horizontally in a wagon accelerating unifor%ly at /.,, %0s#. The bo$ does not %ove relative to the wagon* the coefficient of static friction between the bo$ and the wagons surface is ,.-,,* and the coefficient of &inetic friction is ,.8,,. The friction force on this bo$ is closest to A) 8', 7. B) ?,., 7. C) -,., 7. D) 8'.? 7. Answer! D "ar! 1
1') n a shuffleboard ga%e* the puc& slides a total of before co%ing to rest. f the coefficient of &inetic friction between the puc& and the horizontal board is ,.#>* what was the initial speed of the puc&3 A) >.1 %0s B) #?., %0s C) -.' %0s D) =./ %0s Answer! A "ar! /1
1/ Copyright + #,1- earson ducation* nc.
1-) A driver in a car traveling at sla%s on the bra&es and s&ids to a stop. f the coefficient of friction between the tires and the horizontal road is ,. >,* how long will the s&id %ar&s be3 A) #- % B) #1 % C) // % D) #8 % Answer! A "ar! #=
1=) Eason ta&es off fro% rest across level water on his 9et
1>) Eason ta&es off fro% rest across level water on his 9et
,, % Answer! A "ar! ',6
1?) Gieran ta&es off fro% rest down a ', % high* 1,( slope on his 9et
, 7 parallel to the surface of the slope. The co%bined %ass of s&is and Gieran is ', &g the fuel %ass is negligible). Gierans speed at the botto% is 8, %0s. 2hat is the coefficient of &inetic friction of his s&is on snow3 A) ,.8= B) ,.'> C) ,.#/ D) ,.#? Answer! A "ar! /8
18 Copyright + #,1- earson ducation* nc.
#,) A factory robot drops a 1, &g co%puter onto a conveyor belt running at /.1 %0s. The %aterials are such that μs 5 ,.', and μ& 5 ,./, between the belt and the co%puter. @ow far is the co%puter dragged before it is riding s%oothly on the belt3 A) 1.- % B) ,.?> % C) #./ % D) /., % Answer! A "ar! ',6
#1) ou push downward on a bo$ at an angle #'( below the horizontal with a force of =', 7. f the bo$ is on a flat horizontal surface for which the coefficient of static friction with the bo$ is ,.=-* what is the %ass of the heaviest bo$ you will be able to %ove3 A) '? &g B) -> &g C) '8 &g D) ># &g Answer! A "ar! /1
##) A person is dragging a pac&ing crate of %ass 1,, &g across a rough horizontal floor where the coefficient of &inetic friction is ,.8,,. @e e$erts a force F sufficient to accelerate the crate forward. At what angle above horizontal should his pulling force be directed in order to achieve the %a$i%u% acceleration3 A) #1.>( B) #=.=( C) /,( D) /8.'( ) 8'( Answer! A "ar! 1
#/) A pac&ing crate rests on a horizontal surface. t is acted on by three horizontal forces! -,, 7 to the left* #,, 7 to the right* and friction. The weight of the crate is 8,, 7. f the -,,<7 force is re%oved* the resultant force acting on the crate is A) zero. B) #,, 7 to the right. C) #,, 7 to the left. D) 8,, 7 to the left. ) i%possible to deter%ine fro% the infor%ation given. Answer! A "ar! 1
1' Copyright + #,1- earson ducation* nc.
#8) A pic&up truc& is %oving at #' %0s with a toolbo$ of %ass m resting on the bed of the truc& #.' % behind the cab. uddenly the bra&es are applied* causing the toolbo$ to slide* and the truc& co%es to a stop in 8.= s. The coefficient of &inetic friction between the toolbo$ and the bed of the truc& is ,.#>. After the bra&es are applied* how %uch ti%e elapses be fore the toolbo$ stri&es the cab3 Answer! 1.8 s "ar! 1
#') Two bo$es are connected by a weightless cord running over a very light frictionless pulley as shown in the figure. Bo$ A* of %ass >., &g* is initially at rest on the top of the table. The coefficient of &inetic friction between bo$ A and the table is ,.1,. Bo$ B has a %ass of 1'., &g* and the syste% begins to %ove 9ust after it is released.
a) Draw the free
1Copyright + #,1- earson ducation* nc.
#-) A rope pulls on the lower bloc& in the figure with a tension force of #, 7. The coefficient of &inetic friction between the lower bloc& and the surface is ,.1-. The coefficient of &inetic friction between the lower bloc& and the upper bloc& is also ,.1-. The pulley has no appreciable %ass or friction. 2hat is the acceleration of the #., &g bloc&3
A) 8.1 %0s# B) '.1 %0s# C) >.8 %0s# D) ?.# %0s# Answer! A "ar! 1
#=) Three ob9ects are connected as shown in the figure. The strings and frictionless pulleys have negligible %asses* and the coefficient of &inetic friction between the #., <&g bloc& and the table is ,.#'. 2hat is the acceleration of the #.,<&g bloc&3
A) #.' %0 B) 1.= %0 C) /.# %0 D) 8., %0 Answer! A "ar! ',6
1= Copyright + #,1- earson ducation* nc.
#>) A syste% co%prised bloc&s* a light frictionless pulley* and connecting ropes is shown in the figure. The ?.,<&g bloc& is on a perfectly s%ooth horizontal table. The surfaces of the 1#<&g bloc& are rough* with between the bloc& and the table. f the '.,<&g bloc& accelerates downward when it is released* find its acceleration.
A) 1., %0s# B) 1.# %0s# C) 1.8 %0s# D) 1.- %0s# ) 1.> %0s# Answer! A "ar! 1
1> Copyright + #,1- earson ducation* nc.
#?) Bloc& A of %ass '., &g and bloc& X are attached to a rope which passes over a pulley* as shown in the figure. An >,<7 force P is applied horizontally to bloc& A* &eeping it in contact with a rough vertical face. The coefficients of static and &inetic friction between the wall and bloc& A are μs 5 ,.8, and μ& 5 ,./,. The pulley is light and frictionless. The %ass of bloc& X is ad9usted until bloc& A %oves upward with an acceleration of 1.- %0s#. 2hat is the %ass of bloc& X 3
A) ?.? &g B) ?./ &g C) >.= &g D) >.1 &g ) =.' &g Answer! A "ar! 1
1? Copyright + #,1- earson ducation* nc.
/,) n the figure* two wooden bloc&s each of ,./, &g %ass are connected by a string that passes over a very light frictionless pulley. ne bloc& slides on a horizontal table* while the other hangs suspended by the string* as shown in the figure. At ti%e t 5 ,* the suspended bloc& is ,.>, % over the floor* and the bloc&s are released fro% rest. After #.' s* the suspended bloc& reaches the floor. 2hat is the coefficient of &inetic friction between the table and the sliding bloc&3
A) ,./' B) ,.'# C) ,.>8 D) ,.-' ) ,.?' Answer! "ar! 1
#, Copyright + #,1- earson ducation* nc.
/1) A 8.,,<&g bo$ sits atop a 1,.,<&g bo$ on a horizontal table. The coefficient of &inetic friction between the two bo$es and between the lower bo$ and the table is ,.-,,* while the coefficient of static friction between these sa%e surfaces is ,.>,,. A horizontal pull to the right is e$erted on the lower bo$* as shown in the figure* and the bo$es %ove together. 2hat is the friction force on the FH bo$3
A) 1?./ 7 to the right B) 1?./ 7 to the left C) #/.' 7 to the right D) /1.8 7 to the right ) /1.8 7 to the left Answer! A "ar! 1
/#) A -., &g bo$ slides down an inclined plane that %a&es an angle of /?( with the horizontal. f the coefficient of &inetic friction is ,.1?* at what rate does the bo$ accelerate down the slope3 A) 8.= %0s# B) '.# %0s# C) '.' %0s# D) -.# %0s# Answer! A "ar! ',6
//) A #,, g hoc&ey puc& is launched up a %etal ra%p that is inclined at a /,( angle. The coefficients of static and &inetic friction between the hoc&ey puc& and the %etal ra%p are μ s 5 ,.8, and μ& 5 ,./,* respectively. The puc&s initial speed is -/ %0s. 2hat vertical height does the puc& reach above its starting point3 A) 1/, % B) #=, % C) #,, % D) -- % Answer! A "ar! ',6
#1 Copyright + #,1- earson ducation* nc.
/8) A #,, g hoc&ey puc& is launched up a %etal ra%p that is inclined at a /,( angle. The coefficients of static and &inetic friction between the hoc&ey puc& and the %etal ra%p are μs 5 ,.8, and μ& 5 ,./,* respectively. The puc&s initial speed is 8.? %0s. 2hat speed does it have when it slides bac& down to its starting point3 A) #.> %0s B) /.' %0s C) 8.# %0s D) 8.? %0s Answer! A "ar! ',6
/') A 8.,,<&g bloc& rests on a /,.,( incline as shown in the figure. f the coefficient of static friction between the bloc& and the incline is ,.=,,* what %agnitude horizontal force F %ust act on the bloc& to start it %oving up the incline3
A) /8., 7 B) '1.1 7 C) '8.= 7 D) >8., 7 ) =-.8 7 Answer! D "ar! 1
/-) A bo$ is sliding down an incline tilted at a 1#.,( angle above horizontal. The bo$ is initially sliding down the incline at a speed of 1.', %0s. The coefficient of &inetic friction between the bo$ and the incline is ,./8,. @ow far does the bo$ slide down the incline before co%ing to rest3 A) ,.?#, % B) #.// % C) 1.=> % D) ,.=#, % ) The bo$ does not stop. t accelerates down the plane. Answer! A "ar! '
## Copyright + #,1- earson ducation* nc.
/=) A ',.,<&g bloc& is being pulled up a 1-.,( slope by a force of #', 7 which is parallel to the slope. The coefficient of &inetic friction between the bloc& and the slope is ,.#,,. 2hat is the %agnitude of the acceleration of the bloc&3 A) ,.'#> %0 B) ,.1'> %0 C) ,.81# %0 D) ,.?>/ %0 ) ,.#-, %0 Answer! C "ar! '
/>) Two bloc&s are connected by a string that goes over an ideal pulley as shown in the figure. Bloc& A has a %ass of /.,, &g and can slide over a rough plane inclined /,.,( to the horizontal. The coefficient of &inetic friction between bloc& A and the plane is ,.8,,. Bloc& B has a %ass of #.== &g. 2hat is the acceleration of the bloc&s3
A) ,./?# %0s# B) 1.?- %0s# C) /.1# %0s# D) './' %0s# ) ,.,, %0s# Answer! A "ar! 1
#/ Copyright + #,1- earson ducation* nc.
/?) The figure shows two pac&ages that start sliding down a #,( ra%p fro% rest a distance along the ra%p fro% the botto%. ac&age A has a %ass of '., &g and a coefficient of &inetic friction ,.#, between it and the ra%p. ac&age B has a %ass of 1, &g and a coefficient of &inetic friction ,.1' between it and the ra%p. @ow long does it ta&e pac&age A to reach the botto%3
A) #.= s B) /., s C) /.# s D) /.' s Answer! A "ar! ',6
8,) n the figure* a T
A) #8- 7 B) /-- 7 C) 8/1 7 D) 1>= 7 ) '/' 7 Answer! C "ar! 1
#8 Copyright + #,1- earson ducation* nc.
81) A #',<&g crate is on a rough ra%p* inclined at /,( above the horizontal. The coefficient of &inetic friction between the crate and ra%p is ,.##. A horizontal force of ',,, 7 is applied to the crate* pushing it up the ra%p. 2hat is the acc eleration of the crate3 A) >.8 %0s# B) 1, %0s# C) 1# %0s# D) 1/ %0s# ) /.8 %0s# Answer! A "ar! 1
8#) Two weights are connected by a %assless wire and pulled upward with a constant speed of 1.', %0s by a vertical pull . The tension in the wire is T see figure). P is closest to
A) #' 7. B) 1#' 7. C) 1>=.' 7. D) #8' 7. ) 1##' 7. Answer! B "ar! 1
8/) The figure shows two forces acting at right angles on an ob9ect. They have %agnitudes #' Copyright + #,1- earson ducation* nc.
5
-./ 7 and 5 #.1 7. 2hat third force will cause the ob9ect to be in equilibriu% acceleration equals zero)3
A) -.- 7 at 1-#( countercloc&wise fro%
1
B) -.- 7 at 1,>( countercloc&wise fro%
1
C) 8.# 7 at 1-#( countercloc&wise fro%
1
D) 8.# 7 at 1,>( countercloc&wise fro%
1
Answer! A "ar! #8
88) The figure shows two forces* each of %agnitude 8.- 7* acting on an ob9ect. The angle between these forces is 8,(* and they %a&e equal angles above and below the horizontal. 2hat third force will cause the ob9ect to be in equilibriu% acceleration equals zero)3
A) >.- 7 pointing to the right B) =., 7 pointing to the right C) 8./ 7 pointing to the right D) /.' 7 pointing to the right Answer! A "ar! ',6
#Copyright + #,1- earson ducation* nc.
8') A traffic light weighing 1,, 7 is supported by two ropes as shown in the figure. The tensions in the ropes are closest to
A) ', 7. B) '- 7. C) -/ 7. D) -- 7. ) >/ 7. Answer! "ar! 1
8-) Two bloc&s are connected by a string that goes over an ideal pulley as shown in the figure and pulls on bloc& A parallel to the surface of the plane. Bloc& A has a %ass of /.,, &g and can slide along a rough plane inclined /,.,( to the horizontal. The coefficient of static friction between bloc& A and the plane is ,.8,,. 2hat %ass should bloc& B have in order to start bloc& A sliding up the plane3
Answer! #.'8 &g "ar! 1
#= Copyright + #,1- earson ducation* nc.
8=) The figure shows a #,,, &g cable car descending a high hill. A counterweight of %ass 1>,, &g on the other side of the hill aids the bra&es in controlling the cable cars speed. The rolling friction of both the cable car and the counterweight are negligible. @ow %uch bra&ing force does the cable car need to descend at constant speed3
A) />,, 7 B) #?,, 7 C) #,,, 7 D) ?>, 7 Answer! A "ar! ',6
8>) A syste% of bloc&s and a frictionless pulley is shown in the figure. Bloc& A has a %ass of #., &g and is on a rough horizontal surface for which μs 5 ,.8, between the surface and bloc& A. The rope pulls horizontally on bloc& A. Bloc& C has a %ass of 1., &g. An e$ternal force P 5 #/., 7* applied vertically to bloc& A* %aintains the syste% at rest as shown in the figure. 2hat is the friction force on bloc& A3
A) -./ 7 B) -.? 7 C) =.' 7 D) '.= 7 ) '.1 7 Answer! A "ar! 1
#> Copyright + #,1- earson ducation* nc.
8?) n the figure* a bloc& of %ass M hangs at rest. The rope that is fastened to the wall is horizontal and has a tension off '# 7. The rope that is fastened to the ceiling has a tension of and %a&es an angle θ with the ceiling. 2hat is the angle θ 3
A) ''( B) /'( C) /,( D) -/( ) 8'( Answer! A "ar! ',6
#? Copyright + #,1- earson ducation* nc.
',) A 1'#,<7 crate is to be held in place on a ra%p that rises at /,.,( above the horizontal see figure). The %assless rope attached to the crate %a&es a ##.,( angle above the surface of the ra%p. The coefficients of friction between the crate and the surface of the ra%p are µ& 5 ,.8', and µs 5 ,.-',. The pulley has no appreciable %ass or friction. 2hat is the IAJIFI weight w that can be used to hold this crate stationary on the ra%p3
Answer! 1/>, 7 "ar! 1
/, Copyright + #,1- earson ducation* nc.
'1) Bloc& A of %ass >., &g and bloc& X are attached to a rope that passes over a pulley. A ',<7 force P is applied horizontally to bloc& A* &eeping it in contact with a rough vertical face. The coefficients of static and &inetic friction between the wall and bloc& A are μs 5 ,.8, and μ& 5 ,./,. The pulley is light and frictionless. n the figure* the %ass of bloc& X is ad9usted until bloc& A descends at constant velocity of 8.=' c%0s when it is set into %otion. 2hat is the %ass of bloc& X 3
A) -.' &g B) =.# &g C) >., &g D) >.> &g ) ?.' &g Answer! A "ar! 1
'#) A #/ &g %ass is connected to a nail on a frictionless table by a %assless string 1./ % long. There is no appreciable friction between the nail and the string. f the tension in the string is '1 7 while the %ass %oves in a unifor% circle on the table* how long does it ta&e for the %ass to %a&e one co%plete revolution3 A) 8.> s B) /.> s C) 8.' s D) '.# s Answer! A "ar! ',6
/1 Copyright + #,1- earson ducation* nc.
'/) A car travels at a steady 8,., %0s around a horizontal curve of radius #,, %. 2hat is the %ini%u% coefficient of static friction between the road and the cars tires that will allow the car to travel at this speed without sliding3 A) 1.#/ B) ,.>1C) ,.=/D) ,.?'# ) ,.--# Answer! B "ar! 1
'8) A car enters a /,,<% radius horizontal curve on a rainy day when the coefficient of static friction between its tires and the road is ,.-,,. 2hat is the %a$i%u% speed at which the car can travel around this curve without sliding3 A) #?.- %0s B) //.1 %0s C) #8.> %0s D) 8#., %0s ) /=.? %0s Answer! D "ar! 1
'') A car drives over a hilltop that has a radius of curvature ,.1#, &% at the top of the hill. At what speed would the car be traveling when it tires 9ust barely lose contact with the road when the car is at the top of the hill3 A) 8'.' %0s B) 81.> %0s C) /8./ %0s D) ##.# %0s ) #=.- %0s Answer! C "ar! 1
'-) A 1,,,<&g car is slowly pic&ing up speed as it goes around a horizontal curve whose radius is 1,, %. The coefficient of static friction between the tires and the road is ,./',. At what speed will the car begin to s&id sideways3 A) ?.#' %0s B) #/.- %0s C) /8./ %0s D) /'., %0s ) 1>.' %0s Answer! "ar! 1
/# Copyright + #,1- earson ducation* nc.
'=) A -,,<&g car is going around a ban&ed curve with a radius of 11, % at a speed of #8.' %0s. 2hat is the appropriate ban&ing angle so that the car stays on its path without the assistance of friction3 A) #?.1( B) 1/.'( C) //.>( D) '-.#( ) -,.?( Answer! A "ar! '
'>) A -,,<&g car traveling at #8.' %0s is going around a curve having a radius of 1#, % that is ban&ed at an angle of #,(. a) s the curve properly ban&ed for the cars speed3 b) 2hat is the %ini%u% coefficient of static friction required between the road and the cars tires so the car does not s&id3 Answer! a) 7o b) ,.1# "ar! 1
'?) A -,,<&g car traveling at /,., %0s is going around a curve having a radius of 1#, % that is ban&ed at an angle of #'.,(. The coefficient of static friction between the cars tires and the road is ,./,,. 2hat is the %agnitude of the force e$erted by friction on the car3 A) 1'?, 7 B) /8/, 7 C) =#8, 7 D) =>#, 7 ) =?' 7 Answer! A "ar! 1
-,) ngineers are designing a curved section of a highway. f the radius of curvature of the curve is at what angle should the curve be ban&ed so that a car traveling at #?., %0s will stay on the road without the aid of frictional forces3 A) #/.?( B) 1-.=( C) #1.,( D) #-.1( Answer! A "ar! ',6
// Copyright + #,1- earson ducation* nc.
-1) The figure shows two wires tied to a /./ &g sphere that revolves in a horizontal circle at constant speed. At this particular speed the tension is the AI in both wires. 2hat is the tension3
A) #8 7 B) /# 7 C) 88 7 D) ## 7 Answer! A "ar! ',6
/8 Copyright + #,1- earson ducation* nc.
-#) The figure shows two wires that are tied to a =1, g %ass that revolves in a horizontal circle at a constant speed of =.' %0s. 2hat is the tension in the upper wire3
A) /8 7 B) #, 7 C) #= 7 D) 81 7 Answer! A "ar! ',6
-/) ;uture space stations will create an artificial gravity by rotating. Consider a cylindrical space station /?, % dia%eter rotating about its central a$is. Astronauts wal& on the inside surface of the space station. 2hat rotation period will provide Knor%alK gravity3 A) #> s B) 8, s C) -./ s D) 8.8 s Answer! A "ar! ',6
/' Copyright + #,1- earson ducation* nc.
-8) A new roller coaster contains a loop
-') A ball of %ass '., &g is suspended by two wires fro% a horizontal ar% that is attached to a vertical shaft* as shown in the figure. The shaft is in unifor% rotation about its a$is. The rate of rotation is ad9usted until the tensions in the two wires are LFAM. At that speed* the radial acceleration of the ball is closest to
A) 8.? %0s#. B) '.? %0s#. C) -.? %0s#. D) =.? %0s#. ) ?.? %0s#. Answer! A "ar! 1
/Copyright + #,1- earson ducation* nc.
--) A roadway for stunt drivers is designed for racecars %oving at a speed of 8, %0s. A curved section of the roadway is a circular arc of #/, % radius. The roadway is ban&ed so that a vehicle can go around the curve with the friction force fro% the road equal to zero. At what angle is the roadway ban&ed3 A) /'( B) /=( C) //( D) /1( ) #?( Answer! A "ar! ',6
-=) A person on a sled coasts down a hill and then goes over a slight rise with speed #.= %0s. The top of this rise can be %odeled as a circle of radius 8.1 %. The sled and occupant have a co%bined %ass of 11, &g. f the coefficient of &inetic friction between the snow and the sled is ,.1,* what friction force is e$erted on the sled by the snow as the sled goes over the top of the rise3 Answer! >> 7 "ar! 1
->) A ;erris wheel has dia%eter of 1, % and %a&es one revolution in >., seconds. A person weighing -=, 7 is sitting on one of the benches attached at the ri% of the wheel. 2hat is the apparent weight that is* the nor%al force e$erted on her by the bench) of the person as she passes through the highest point of her %otion3 Answer! 8-, 7 "ar! 1
-?) The %agnitude of the drag force of air resistance on a certain #,.,<&g ob9ect is proportional to its speed. f the ob9ect has a ter%inal speed >,., %0s* what is the %agnitude of the drag force on the ob9ect when it is falling with a speed /,., %0s3 A) 1?- 7 B) =.', 7 C) 1'., 7 D) =/.' 7 ) 8#.= 7 Answer! D "ar! 1
/= Copyright + #,1- earson ducation* nc.
=,) A /,.,<&g ob9ect e$periences a drag force due to air resistance with a %agnitude proportional to the square of its speed. The ob9ect falls with an acceleration of 8.,, %0s# downward when it is falling downward at =,., %0s. 2hat is its ter%inal speed3 A) 11, %0s B) 1'= %0s C) ?1., %0s D) 1=# %0s ) 1,> %0s Answer! C "ar! 1
=1) A ship is being pulled through a harbor at constant velocity by two tugboats as shown in the figure. The lines attached to the two tugboats have the sa%e tension of #,,*,,, 7. ach line %a&es an angle of #>.,( with the direction the ship is being towed. 2hat is the %agnitude of the drag force due to the water on the ship3
A) 1== N 1,' 7 B) 1.>> N 1,' 7 C) ?/.? N 1,8 7 D) zero ) /.'/ N 1,' 7 Answer! "ar! 1
=#) A 1.#,<&g ball is hanging fro% the end of a rope. The rope hangs at an angle #'.,( fro% the vertical when a 1'., %0s horizontal wind is blowing. f the winds force on the rope is negligible* what drag force does the wind e$ert on the ball3 A) /#./ 7 B) #8.1 7 C) /.-> 7 D) '.8> 7 ) 11.> 7 Answer! D "ar! 1
/> Copyright + #,1- earson ducation* nc.
