Chapter: Chapter 7 Learning Objectives LO 7.1.0 Solve problems related to kinetic energy LO 7.1.1 Apply the relationship beteen a particle!s kinetic energy" energy" mass" and speed. LO 7.1.# $denti%y that kinetic energy is a scalar &'antity. LO 7.#.0 Solve problems related to ork and kinetic energy LO 7.#.1 Apply the relationship beteen a %orce (magnit'de and direction) and the ork done on a particle by the %orce hen the particle 'ndergoes a displacement. LO 7.#.# Calc'late ork by taking a dot prod'ct o% the %orce vector and the displacement vector" in either magnit'de*angle or 'nit*vector notations. LO 7.#.+ $% m'ltiple %orces act on a particle" calc'late the net ork done by them. LO 7.#., Apply the ork-kinetic energy theorem to relate the ork don e by a %orce and the res'lting change in kinetic energy. LO 7.+.0 Solve problems related to ork done by the gravitational %orce LO 7.+.1 Calc'late the ork done by the gravitational %orce hen an object is li%ted or loered. LO 7.+.# Apply the ork-kinetic energy theorem to sit'ations here an object is li%ted or loered. LO 7.,.0 Solve problems related to ork done by a spring %orce LO 7.,.1 Apply the relationship (ooke!s la) la) beteen the %orce on an object by a spring" the stretch or compression o% the spring" and the spring co nstant o% the spring. LO 7.,.# $denti%y that a spring %orce is a variable %orce. LO 7.,.+ Calc'late the ork done on an object by a spring %orce by integrating the %orce %rom the initial position to the %inal position o% the object or b y 'sing the knon generic res'lt o% that integration. LO 7.,., Calc'late the ork by graphically integrating on a graph o% %orce vers's position o% the object. LO 7.,./ Apply the ork-kinetic energy theorem to sit'ations in hich an object is moved by a spring %orce. LO 7./.0 Solve problems related to ork done by a general variable %orce LO 7./.1 iven a variable %orce as a %'nction o% position" calc'late the ork done by it on an object by integrating the %'nction %rom the initial to the %inal position o% the object" in one or more dimensions. LO 7./.# iven a graph o% %orce vers's position" calc'late the ork done by graphically integrating %rom the initial to the %inal position o% the object. LO 7./.+ Convert a graph o% acceleration vers's position to a graph o% %orce vers's position. LO 7./., Apply the ork-kinetic energy theorem to sit'ations here an object is moved by a variable %orce.
LO 7..0 Solve problems related to poer
LO 7..1 Apply the relationship beteen average poer" the ork done b y a %orce" and the time interval in hich that ork is done. LO 7..# iven the ork as a %'nction o% time" %ind the instantaneo's p oer. LO 7..+ 2etermine the instantaneo's poer by taking the dot prod'ct o% the %orce vector and an object!s velocity vector" in magnit'de*angle and 'nit*vector notations. 3'ltiple Choice 1. 4hich o% the %olloing %olloing bodies has the largest largest kinetic energy5 A) 3ass + M and and speed V 6) 3ass + M and and speed #V #V C) 3ass # M and and speed +V +V 2) 3ass M 3ass M and and speed ,V ,V ) All %o'r o% the above have the same kinetic energy Ans: C 2i%%ic'lty: Section: 7*1 Learning Objective 7.1.1 #. 8o 8o trailers" 9 ith mass /00 kg and ith mass #000 kg" are being p'lled at the same speed. 8he ratio o% the kinetic energy o% to that o% 9 is: A) 1:1 6) #:1 C) ,:1 2) ;:1 ) 1/00:1 Ans: C 2i%%ic'lty: Section: 7*1 Learning Objective 7.1.1 +. An <000*= car is traveling at 1# m>s along a hori?ontal road hen the brakes are applied. 8he car skids to a stop in ,.0 s. o m'ch kinetic energy does the car lose in this time5 A) ,.< × 10, @ 6) /.; × 10, @ C) 1.# × 10/ @ 2) /.< × 10/ @ ) ,.< × 10 @ Ans: 6 2i%%ic'lty: Section: 7*1 Learning Objective 7.1.1
,. An object is constrained by a cord to move in a circ'lar path o% radi's 0./m on a hori?ontal %rictionless s'r%ace. 8he cord ill break i% its tension eceeds 1=. 8he maim'm kinetic energy the object can have is: A) , @ 6) < @ C) 1 @ 2) +# @ ) , @ Ans: A 2i%%ic'lty: 3 Section: 7*1 Learning Objective 7.1.1 /. 8he eight o% an object on the moon is one*sith o% its eight on the arth. 8he ratio o% the kinetic energy o% a body on the arth moving ith speed V to that o% the same body moving ith speed V on the moon is: A) :1 6) +:1 C) 1:1 2) 1: ) 1:+ Ans: C 2i%%ic'lty: Section: 7*1 Learning Objective 7.1.1 . 4hich o% the %olloing is the correct combination o% dimensions %or energy5 A) 3L8 6) L8# >3 C) 3L#>8# 2) 3#L+8 ) 3L>8# Ans: C 2i%%ic'lty: Section: 7*1 Learning Objective 7.1.1 7. 4hich o% the %olloing is =O8 a correct 'nit %or ork5 A) erg 6) %t⋅lb C) att 2) neton⋅meter ) jo'le
Ans: C 2i%%ic'lty: Section: 7*# Learning Objective 7.#.0
<. 4hich o% the %olloing gro'ps does =O8 contain a scalar &'antity5 A) velocity" %orce" energy 6) displacement" acceleration" %orce C) acceleration" speed" energy 2) energy" %orce" distance ) energy" eight" time Ans: 6 2i%%ic'lty: Section: 7*1 Learning Objective 7.1.# ;. A boy holds a ,0*= eight at armBs length %or 10 s. is arm is 1./ m above the gro'nd. 8he ork done by the %orce o% the boy on the eight hile he is holding it is: A) 0 @ 6) .1 @ C) ,0 @ 2) 0 @ ) ;0 @ Ans: A 2i%%ic'lty: Section: 7*# Learning Objective 7.#.1 10. A crate moves 10 m to the right on a hori?ontal s'r%ace as a oman p'lls on it ith a 10*= %orce. ank the sit'ations shon belo according to the ork done by her %orce" least to greatest.
A) 1"#"+ 6) #"1"+ C) #"+"1
2) 1"+"# ) +"#"1" Ans: 2i%%ic'lty: Section: 7*# Learning Objective 7.#.1 11. A #*kg object is moving at + m>s. A ,*= %orce is applied in the direction o% motion and then removed a%ter the object has traveled an additional / m. 8he ork done by this %orce is: A) ; @ 6) 1< @ C) #0 @ 2) #; @ ) +< @ Ans: C 2i%%ic'lty: Section: 7*# Learning Objective 7.#.1 1#. A sledge (incl'ding load) eighs /000 =. $t is p'lled on level sno by a dog team eerting a hori?ontal %orce on it. 8he coe%%icient o% kinetic %riction beteen sledge and sno is 0.0/. o m'ch ork is done by the dog team p'lling the sledge 1000 m at constant speed5 A) 0 @ 6) #./ × 10/ @ C) /.0 × 10/ @ 2) #./ × 10 @ ) /.0 × 10 @ Ans: 6 2i%%ic'lty: 3 Section: 7*# Learning Objective 7.#.1 1+. Camping e&'ipment eighing 000 = is p'lled across a %ro?en lake by means o% a hori?ontal rope. 8he coe%%icient o% kinetic %riction is 0.0/. 8he ork done by the campers in p'lling the e&'ipment 1000 m at constant velocity is: A) 0 @ 6) 1./ × 10/ @ C) +.0 × 10/ @ 2) #.; × 10 @ ) .0 × 10 @ Ans: C
2i%%ic'lty: 3 Section: 7*# Learning Objective 7.#.1 1,. Camping e&'ipment eighing 000 = is p'lled across a %ro?en lake by means o% a hori?ontal rope. 8he coe%%icient o% kinetic %riction is 0.0/. o m'ch o rk is done by the campers in p'lling the e&'ipment 1000 m i% its speed is increasing at the constant rate o% 0.#0 m>s#5 A) -1.# × 10 @ 6) 1.# × 10/ @ C) +.0 × 10/ @ 2) ,.# × 10/ @ ) ,.1 × 10 @ Ans: 2 2i%%ic'lty: 3 Section: 7*# Learning Objective 7.#.1 1/. A 0./0*kg object moves in a hori?ontal circ'lar track ith a radi's o% #./ m. An eternal %orce o% +.0 =" alays tangent to the track" ca'ses the object to speed 'p as it goes aro'nd. 8he ork done by the eternal %orce as the mass makes one revol'tion is: A) 7./ @ 6) #, @ C) ,7 @ 2) ;, @ ) 1#0 @ Ans: C 2i%%ic'lty: Section: 7*# Learning Objective 7.#.1 1. A crate is initially at rest on a hori?ontal %rictionless table. A constant hori?ontal %orce F is applied. 4hich o% the %olloing %ive graphs is a correct plot o% ork 4 as a %'nction o% crate speed v5
A) 6) C) 2) )
$ $$ $$$ $D D
Ans: 2 2i%%ic'lty: 3 Section: 7*# Learning Objective 7.#.1 17. An object moves in a circle at constant speed. 8he ork done by the centripetal %orce is ?ero beca'se: A) the displacement %or each revol'tion is ?ero 6) the average %orce %or each revol'tion is ?ero C) there is no %riction 2) the magnit'de o% the acceleration is ?ero ) the centripetal %orce is perpendic'lar to the velocity Ans: 2i%%ic'lty: Section: 7*# Learning Objective 7.#.# 1<. An object o% mass 1 kg is hirled in a hori?ontal circle o% radi's 0./ m at a constant speed o% # m>s. 8he ork done on the object d'ring one revol'tion is: A) 0 @ 6) 1 @ C) # @ 2) , @ ) 1 @ Ans: A 2i%%ic'lty: Section: 7*#
Learning Objective 7.#.# 1;. A particle moves / m in the positive x direction hile being acted 'pon by a constant %orce ^ F E (, =) i F (# = j ) - (, =) k . 8he ork done on the particle by this %orce is: ^
A) 6) C) 2) )
^
#0 @ 10 @ -#0 @ +0 @ is impossible to calc'late itho't knoing other %orces
Ans: A 2i%%ic'lty: Section: 7*# Learning Objective 7.#.# #0. A man p'lls a sled along a ro'gh hori?ontal s'r%ace by applying a constant %orce
F
at an
angle θ above the hori?ontal. $n p'lling the sled a hori?ontal distance d " the ork done by the man is: A) Fd 6) Fd cos θ C) Fd sin θ 2) Fd >cos θ ) Fd >sin θ Ans: 6 2i%%ic'lty: Section: 7*# Learning Objective 7.#.# #1. A 100*kg piano rolls don a #0G incline. A man tries to keep it %rom accelerating" and manages to keep its acceleration to 1.# m>s#. $% the piano rolls / m" hat is the net ork done on it by all the %orces acting on it5 A) 0 @ 6) 100 @ C) 00 @ 2) 1000 @ ) ,;00 @ Ans: C 2i%%ic'lty: 3 Section: 7*# Learning Objective 7.#.+ ##. An <*= block slides don an incline. $t has an initial speed o% 7 m>s. 8he ork done by the
res'ltant %orce on this block is: A) #0 @ 6) #< @ C) / @ 2) impossible to calc'late itho't more in%ormation ) none o% these Ans: 2 2i%%ic'lty: Section: 7*# Learning Objective 7.#.+ #+. 8he mechanical advantage o% any machine is: A) the e%%iciency o% the machine 6) the ork done by the machine C) the ratio o% the ork done by the machine to the ork epended on it 2) the ratio o% the %orce eerted by the machine to the %orce applied to it ) the ratio o% the %orce applied to the machine to the %orce eerted by it Ans: 2 2i%%ic'lty: Section: 7*# Learning Objective 7.#.0 #,. $n raising an object to a given height by means o% an inclined plane" as compared ith raising the object vertically" there is a red'ction in: A) ork re&'ired 6) distance p'shed C) %riction 2) %orce re&'ired ) val'e o% the acceleration d'e to gravity Ans: 2 2i%%ic'lty: Section: 7*# Learning Objective 7.#.0 #/. 8o objects ith masses" m1 and m#" have the same kinetic energy and are both moving to the right. 8he same constant %orce F is applied to the le%t to both masses. $% m E ,m " the 1
ratio o% the stopping distance o% m1 to that o% m# is: A) 1:, 6) ,:1 C) 1:# 2) #:1 ) 1:1
#
Ans: 2i%%ic'lty: 3 Section: 7*# Learning Objective 7.#., #. At time t E 0 a particle starts moving along the x ais. $% its kinetic energy increases 'ni%ormly ith t the net %orce acting on it m'st be: A) constant 6) proportional to t C) inversely proportional to t 2) proportional to √ t ) proportional to 1> √ t Ans: 2i%%ic'lty: 3 Section: 7*# Learning Objective 7.#., ^ #7. At time t E 0 a #*kg particle has a velocity o% (, m>s) i - (+ m>s) j . At t E + s its ^
velocity is (# m>s) A) 6) C) 2)
,@ -, @ -1# @ -,0 @
) (, @)
i ^
i ^
^ F (+ m>s) j . 2'ring this time the ork done on it as:
^ F (+ @) j
Ans: C 2i%%ic'lty: 3 Section: 7*# Learning Objective 7.#., #<. A particle starts %rom rest at time t E 0 and moves along the x ais. $% the net %orce on it is proportional to t " its kinetic energy is proportional to: A) t 6) t # C) t , 2) 1>t # ) none o% the above Ans: C 2i%%ic'lty: Section: 7*# Learning Objective 7.#.,
#;. 8he velocity o% a particle moving along the x ais changes %rom vi to v f . Hor hich val'es o% vi and v f is the total ork done on the particle positive5 A) vi E /m>s" v f E #m>s 6) vi E /m>s" v f E -#m>s C) vi E -/m>s" v f E -#m>s 2) vi E -/m>s" v f E #m>s ) vi E -#m>s" v f E -/m>s Ans: 2i%%ic'lty: Section: 7*# Learning Objective 7.#., +0. 8he amo'nt o% ork re&'ired to stop a moving object is e&'al to the: A) velocity o% the object 6) kinetic energy o% the object C) mass o% the object times its acceleration 2) mass o% the object times its velocity ) s&'are o% the velocity o% the object Ans: 6 2i%%ic'lty: Section: 7*# Learning Objective 7.#., +1. A /.0*kg cart is moving hori?ontally at .0 m>s. $n order to change its speed to 10.0 m>s" the net ork done on the cart m'st be: A) #0 @ 6) ,0 @ C) ;0 @ 2) 10 @ ) ,00 @ Ans: 2 2i%%ic'lty: Section: 7*# Learning Objective 7.#., +#. A ,*kg cart starts 'p an incline ith a speed o% + m>s and comes to rest # m 'p the incline. 8he total ork done on the cart is: A) - @ 6) -< @ C) -1# @ 2) -1< @ ) impossible to calc'late itho't more in%ormation
Ans: 2 2i%%ic'lty: Section: 7*# Learning Objective 7.#., ++. A 6oston ed So baseball player catches a ball o% massm that is moving toard him ith speed v. 4hile bringing the ball to rest" his hand moves b ack a distance d . Ass'ming constant deceleration" the hori?ontal %orce eerted on the ball by his hand is: A) mv>d 6) mvd C) mv#>d 2) #mv>d ) mv#>(#d ) Ans: 2i%%ic'lty: Section: 7*# Learning Objective 7.#., +,. A 0./0*kg object moves in a hori?ontal circ'lar track ith a radi's o% #./ m. An eternal %orce o% +.0 =" alays tangent to the track" ca'ses the object to speed 'p as it goes aro'nd. $% it starts %rom rest its speed at the end o% one revol'tion is: A) /./ m>s 6) 1, m>s C) 1/ m>s 2) 1< m>s ) #1 m>s Ans: 6 2i%%ic'lty: Section: 7*# Learning Objective 7.#., +/. A 0./0*kg object moves on a hori?ontal %rictionless circ'lar track ith a radi's o% #./ m. An eternal %orce o% +.0 =" alays tangent to the track" ca'ses the object to speed 'p as it goes aro'nd. $% it starts %rom rest" then at the end o % one revol'tion the radial component o% the %orce o% the track on it is: A) 1; = 6) +< = C) ,7 = 2) 7/ = ) ; = Ans: 6 2i%%ic'lty: 3
Section: 7*# Learning Objective 7.#., +. An <0*= crate slides ith constant speed a distance o% /.0 m donard along a ro'gh slope that makes an angle o% +0° ith the hori?ontal. 8he ork done b y the %orce o% gravity is: A) -,00 @ 6) -#00 @ C) -; @ 2) #00 @ ) ,00 @ Ans: 2 2i%%ic'lty: Section: 7*+ Learning Objective 7.+.1 +7. A 1*kg block is li%ted vertically 1 m at constant speed by a boy. 8he ork done by the boy is abo't: A) 1 %t ⋅lb 6) 1 @ C) 10 @ 2) 0.1 @ ) 0 @ Ans: C 2i%%ic'lty: Section: 7*+ Learning Objective 7.+.1 +<. 8he ork done by gravity d'ring the descent o% a projectile is: A) positive 6) negative C) ?ero 2) depends %or its sign on the direction o% the y ais ) depends %or its sign on the direction o% both the x and y aes Ans: A 2i%%ic'lty: Section: 7*+ Learning Objective 7.+.1 +;. A man p'lls a 100*= crate 'p a %rictionless +0° slope / m high as shon. Ass'ming that the crate moves at constant speed" the ork done by the man is:
A) 6) C) 2) )
-/00 @ -#/0 @ 0@ #/0 @ /00 @
Ans: 2i%%ic'lty: Section: 7*+ Learning Objective 7.+.1 ,0. A man p'shes an <0*= crate a distance o% /.0 m 'pard along a %rictionless slope that makes an angle o% +0° ith the hori?ontal. is %orce is parallel to the slope. $% the speed o% the crate decreases at a rate o% 1./ m>s#" then the ork done by the man is: A) -#00 @ 6) 1 @ C) 1,0 @ 2) #00 @ ) ,00 @ Ans: C 2i%%ic'lty: 3 Section: 7*+ Learning Objective 7.+.1 ,1. A man p'shes an <0*= crate a distance o% /.0 m 'pard along a %rictionless slope that makes an angle o% +0° ith the hori?ontal. 8he %orce he eerts is parallel to the slope. $% the speed o% the crate is constant" then the ork done by the man is: A) -#00 @ 6) 1 @ C) 1,0 @ 2) #00 @ ) #0 @ Ans: 2 2i%%ic'lty: 3 Section: 7*+ Learning Objective 7.+.1 ,#. A man moves the 10*g object shon in a vertical plane at a constant speed %rom position 9 to position along a circ'lar track o% radi's #0 m. 8he process takes 0.7/ min. 8he ork done
by the man is abo't:
A) 6) C) 2) )
1@ #@ ,@ @ 1# @
Ans: C 2i%%ic'lty: Section: 7*+ Learning Objective 7.+.1 ,+. A oman li%ts a barbell #.0 m in /.0 s. $% she li%ts it the same distance in 10 s" the ork done by her is: A) %o'r times as great 6) to times as great C) the same 2) hal% as great ) one*%o'rth as great Ans: C 2i%%ic'lty: Section: 7*+ Learning Objective 7.+.1 ,,. A line drive to the shortstop is ca'ght at the same height as it as originally hit. Over its entire %light the ork done by gravity and the ork done by air resistance" respectively" are: A) ?eroI positive 6) ?eroI negative C) positiveI negative 2) negativeI positive ) negativeI negative Ans: 6 2i%%ic'lty: Section: 7*+ Learning Objective 7.+.# ,/. A baseball is hit high into the 'pper bleachers o% le%t %ield. Over its entire %light the ork
done by gravity and the ork done by air resistance" respectively" are: A) positiveI positive 6) positiveI negative C) negativeI positive 2) negativeI negative ) 'nknon since vital in%ormation is lacking Ans: 2 2i%%ic'lty: Section: 7*+ Learning Objective 7.+.# ,. A block is attached to the end o% an ideal spring and moved %rom coordinate xi to coordinate x f . 8he relaed position is at x E 0. 8he ork done by spring is positive i%: A) xi E # cm and x f E , cm 6) xi E -# cm and x f E , cm C) xi E -# cm and x f E -, cm 2) xi E # cm and x f E -, cm ) xi E -, cm and x f E -# cm Ans: 2i%%ic'lty: Section: 7*, Learning Objective 7.,.1 ,7. An ideal spring" ith a pointer attached to its end" hangs net to a scale. 4ith a 100*= eight attached" the pointer indicates J,0J on the scale as shon. Ksing a #00*= eight instead res'lts in J0J on the scale. Ksing an 'nknon eight 9 instead res'lts in J+0J on the scale. 8he eight o% 9 is:
A) 6) C) 2) )
#0 = +0 = ,0 = /0 = 7/ =
Ans: 2 2i%%ic'lty: 3 Section: 7*,
Learning Objective 7.,.1 ,<. A spring o% spring constant k is attached to a block o% mass m. 8he spring moves the block thro'gh a displacement x. o can yo' calc'late ho m'ch ork the spring does on the block5 A) 3'ltiply the spring %orce" kx" by the distance x. 6) 3'ltiply the spring %orce" kx#" by the distance x. C) $ntegrate the spring %orce" kx" over the distance x. 2) $ntegrate the spring %orce" kx#" over the time it takes the block to move. ) o' cannot calc'late this itho't knoing the acceleration o% the block. Ans: C 2i%%ic'lty: Section: 7*, Learning Objective 7.,.# ,;. 8his plot shos an object being moved by a series o% %orces. 4hich segments o% the motion co'ld have been ca'sed by %ied springs5
A) =one o% the segments co'ld represent ork being done by springs. 6) Any o% the segments co'ld represent ork being done b y springs. C) Segments A and C only. 2) Segments 6 and 2 only. ) Segment A only. Ans: C 2i%%ic'lty: Section: 7*, Learning Objective 7.,.# /0. An ideal spring is h'ng vertically %rom the ceiling. 4hen a #.0*kg mass hangs at rest %rom it" the spring is etended .0 cm %rom its relaed length. A donard eternal %orce is no applied to the mass to etend the spring an additional 10 cm. 4hile the spring is being etended by the %orce" the ork done by the spring is: A) -+. @
6) C) 2) )
-+.+ @ -1.0 @ +.+ @ +. @
Ans: A 2i%%ic'lty: 3 Section: 7*, Learning Objective 7.,.+ /1. 8hree identical springs (9" " M) are arranged as shon. 4hen a ,.0*kg mass is h'ng on 9" the mass descends +.0 cm. 4hen a .0*kg mass is h'ng on " the mass descends:
A) 6) C) 2) )
#.0 cm ,.0 cm ,./ cm .0 cm ;.0 cm
Ans: 2i%%ic'lty: 3 Section: 7*, Learning Objective 7.,.+ /#. An ideal spring is h'ng vertically %rom the ceiling. 4hen a #.0*kg mass hangs at rest %rom it" the spring is etended .0 cm %rom its relaed length. An 'pard eternal %orce is then applied to the block to move it 'pard a distance o% 1 cm. 4hile the block is being raised by the %orce" the ork done by the spring is A) -1.0 @ 6) -0./# @ C) -0.# @ 2) 0./# @ ) 1.0 @ Ans: A 2i%%ic'lty: 3 Section: 7*, Learning Objective 7.,.+
/+. 4hen a certain r'bber band is stretched a distance x" it eerts a restoring %orce o% magnit'de F E Ax" here A is a constant. 8he ork done by a person in stretching this r'bber band %rom x E 0 to x E L is: A) AL# 6) AL C) A F # L# 2) A> L ) AL#># Ans: 2i%%ic'lty: 3 Section: 7*, Learning Objective 7.,.+ /,. $n the plot shon o% %orce vs. distance" approimately ho m'ch ork is done in moving an object %rom x E / m to x E 1/ m5
A) 10 @ 6) // @ C) 1#/ @ 2) #7/ @ ) cannot be calc'lated itho't knoing the mass o% the object Ans: 2 2i%%ic'lty: Section: 7*, Learning Objective 7.,., //. A #*kg block is attached to a hori?ontal ideal spring ith a spring constant o% #00 =>m. 4hen the spring has its e&'ilibri'm length the block is given a speed o% / m>s. 4hat is the maim'm elongation o% the spring5 A) 0 m 6) 0./ m C) / m
2) 10 m ) 100 m Ans: 6 2i%%ic'lty: Section: 7*, Learning Objective 7.,./ /. A 1./ kg crate %alls %rom a height o% #.0 m onto an ind'strial spring scale ith a spring constant o% 1./ × 10/ =>m. At its greatest compression the reading on the scale is: A) 1/ = 6) #; = C) 1./ × 10+ = 2) #.1 × 10+ = ) +.0 × 10+ = Ans: 2i%%ic'lty: 3 Section: 7*, Learning Objective 7.,./ /7. 4hen a certain r'bber band is stretched a distance x" it eerts a restoring %orce F E ax F bx#" here a and b are constants. 8he ork done in stretching this r'bber band %rom x E 0 to x E L is: A) aL# F bLx+ 6) aL F #bL# C) a F #bL 2) bL ) aL#># F bL+>+ Ans: 2i%%ic'lty: 3 Section: 7*/ Learning Objective 7./.1 /<. 8he plot shos the %orce on an object as it moves %rom x E 0 m to x E #0 m. o m'ch ork is done on the object5
A) ,0 @ 6) ;0 @ C) #00 @ 2) ,/0 @ ) 7/0 @ Ans: 2 2i%%ic'lty: Section: 7./ Learning Objective 7./.# /;. A particle moving along the x ais is acted 'pon by a single %orce F E F 0e –kx" here F 0 and k are constants. 8he particle is released %rom rest at x E 0. $t ill attain a maim'm kinetic energy o%: A) F 0>k 6) F 0>ek C) kF 0 2) 1>#(kF 0)# ) kek F 0 Ans: A 2i%%ic'lty: 3 Section: 7*/ Learning Objective 7./., 0. One att is: A) 1 kg ⋅ m>s+ 6) 1 kg ⋅ m#>s C) 1 kg ⋅ m#>s+ 2) 1 kg ⋅ m>s ) 1 kg ⋅ m#>s# Ans: C 2i%%ic'lty: Section: 7* Learning Objective 7..0
1. Noer has the dimensions o%: A) 3L#>8# 6) 38>L# C) 3L>8# 2) 3L#>8+ ) none o% these Ans: 2 2i%%ic'lty: Section: 7* Learning Objective 7..0 #. An escalator is 'sed to move #0 people (0 kg each) per min'te %rom the %irst %loor o% a department store to the second %loor" / m above. 8he po er re&'ired is approimately:
A) 6) C) 2) )
100 4 #00 4 1000 4 #000 4 0"000 4
Ans: C 2i%%ic'lty: Section: 7* Learning Objective 7..1 +. A person holds an <0*= eight # m above the %loor %or +0 seconds. 8he poer re&'ired to do this is: A) /.+ 4 6) ,0 4 C) <0 4 2) 10 4 ) none o% these Ans: 2i%%ic'lty: Section: 7* Learning Objective 7..1
,. A /0*= %orce acts on a #*kg crate that starts %rom rest. 4hen the %orce has been acting %or # s the rate at hich it is doing ork is: A) 100 4 6) 1000 4 C) #/00 4 2) /000 4 ) +000 4 Ans: C 2i%%ic'lty: 3 Section: 7* Learning Objective 7..# /. A /0*= %orce is the only %orce on a #*kg crate that starts %rom rest. At the instant the crate has gone # m the rate at hich the %orce is doing ork is: A) #./ 4 6) #/ 4 C) 7/ 4 2) 100 4 ) /00 4 Ans: 2i%%ic'lty: 3 Section: 7* Learning Objective 7..# . 4hich o% the %olloing %ive 'nits represents a &'antity that is =O8 the same type as the other %o'r5 A) jo'le 6) erg C) att 2) %oot⋅ po'nd ) neton⋅meter Ans: C 2i%%ic'lty: Section: 7* Learning Objective 7..0 7. 4hich o% the %olloing %ive &'antities is =O8 an epression %or energy5 ere m is a mass" g is the acceleration d'e to gravity" h and d are distances" F is a %orce" v is a speed" a is an acceleration" P is poer" and t is time. A) mgh 6) Fd C) 1>#mv# 2) ma
) Pt Ans: 2 2i%%ic'lty: Section: 7* Learning Objective 7..0 <. A att ⋅second is a 'nit o%: A) %orce 6) poer C) displacement 2) speed ) energy Ans: 2i%%ic'lty: Section: 7* Learning Objective 7..0
;. A att per ho'r is a 'nit o%: A) energy 6) poer C) %orce 2) acceleration ) none o% these Ans: 2i%%ic'lty: Section: 7* Learning Objective 7..0 70. A kiloatt ho'r is a 'nit o%: A) poer 6) energy>time C) energy 2) poer>time ) %orce>distance Ans: C 2i%%ic'lty: Section: 7* Learning Objective 7..0
71. A particle starts %rom rest and is acted on by a net %orce that does ork at a rate that is
proportional to the time t . 8he speed o% the particle is proportional to: A) √ t 6) t C) t # 2) 1> √ t ) 1>t Ans: A 2i%%ic'lty: 3 Section: 7* Learning Objective 7..0
7#. A %orce
F
E (,.1 =)
i ^
^ F (#. = j ) - (,.7 =) k acts on a mass o% #.+ kg as it moves ^
in the x direction at a speed o% 7.# m>s. 4hat is the rate at hich the %orce is doing ork5 A) <.< 4 6) 1 4 C) +0 4 2) ,; 4 ) 0 4 Ans: C 2i%%ic'lty: Section: 7* Learning Objective 7..+ 7+. A mass o% ,7 kg is moving hori?ontally as a %orce o% 1;0 =" directed at #/G belo the hori?ontal" is eerted on it. 4hen its speed is 7.+ m>s" hat is the rate at hich the %orce is doing ork5 A) 0 4 6) +,0 4 C) /;0 4 2) 1+00 4 ) 1,00 4 Ans: 2 2i%%ic'lty: Section: 7* Learning Objective 7..+
