University of the Philippines College of Science
Physics 71
Set A Final Exam First Semester, AY 2013–2014
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Final Exam
First Semester, AY 2013–2014
Physics 71
Instruction: Choose the letter of the best answer to each of the following questions.To change your answer, cross (X) out the shaded letter and supply your new answer with your signature beside the item. Cheating is punishable by expulsion.
mSun = 1.99 × 1030 kg mEarth = 5.97 × 1024 kg rEarth = 6.38 × 106 m m G = 6.67 × 10 11 N · kg
P atm = 1.013 × 105 Pa ρwater = 1.00 × 103 kg m ρseawater = 1.03 × 103 kg m 3
3
2
−
2
1. Brick. A brick is dropped from rest on a 30.6 m tall building. Ignoring air resistance, what is its speed just before it hits the ground? A. 12.2 m / s
C. 24.5 m / s
B. 18.3 m / s
D. 32.6 m / s
E. 44.8 m / s
2. Brake, Manong! A truck is initially moving at +10 m/s ˆi when a red light forces the driver to come to a complete stop. What is the average acceleration of the truck if it travelled 10 m before stopping? A. +2 m/s ˆi 2
B.
−
2 m/s ˆi 2
C. +5 m/s ˆi 2
D.
−
5 m/s ˆi
A– 2
2
E.
−
10 m/s ˆi 2
Final Exam
First Semester, AY 2013–2014
Physics 71
3. Man vs bear. A man and a bear starting from rest runs at constant acceleration, but the magnitude of the bear’s acceleration is twice that of the man. Compared to the man, how much farther would the bear have traveled? A. two times as far
C. 1.4 times as far
B. three times as far
D. four times as far
E. one-half as far
4. PROjectiles. Which of the following vector components are CONSTANT for projectile motion? I. Vertical component of acceleration
III. Vertical component of velocity
II. Horizontal position
IV. Horizontal component of velocity
A. I and II only
D. II and III only
B. I and III only
E. III and IV only
C. I and IV only 5. Train. A cyclist is resting near a train track. A train passes by with a velocity of 3 .0 m/s ˆi with respect to the ground. A passenger is walking with a velocity of 1.0 m/s ˆi with respect to the train. What is the passenger’s velocity with respect to the cyclist? A. 2 m/s ˆi
B. 3 m/s ˆi
C. 4 m/s ˆi
D. 5 m/s ˆi
E. 6 m/s ˆi
6. Excite Bike. The world-record motorcycle jump has a range of 77.0 m. If the motorist left the take-off ramp at 12.0◦ above the horizontal and the take-off and landing heights are the same, what is his take-off speed? A. 13.8 m/s
C. 28.7 m/s
B. 19.2 m/s
D. 43.1 m/s
E. 60.2 m/s
7. Ball. A ball is initially launched horizontally at the speed of 10 .0 m/s from the top of the building 56.0 m tall. How long is the ball in the air? A. 2.51 s
B. 3.38 s
C. 3.87 s
A– 3
D. 4.55 s
E. 5.91 s
Final Exam
First Semester, AY 2013–2014
Physics 71
8. Leaving from a jetplane. While a jetplane travels with velocity 122 m/s jˆ relative to the ˆ relative to the ground, Steve leaps from the jetplane with velocity 1 .00 m/s ˆi + 1.50 m/s k jetplane. What is Steve’s velocity relative to the ground?
ˆ j + 1.00 m/s ˆi + 1.50 m/s k A. 122 m/s ˆ ˆ j − 1.00 m/s ˆi − 1.50 m/s k B. 122 m/s ˆ ˆ 122 m/s ˆ j + 1.00 m/s ˆi + 1 .50 m/s k ˆ j − 1.00 m/s ˆi − 1.50 m/s k D. −122 m/s ˆ ˆ E. 1.00 m/s ˆi + 1.50 m/s k C.
−
9. Law. Which of the following statements is/are TRUE regarding Newton’s Laws? I. Newton’s 2nd law can be applied to non-inertial frames of reference. II. A body can be in equilibrium even if it is moving. III. Action-reaction forces act in the same direction. A. I only
C. III only
B. II only
D. I and II only
E. I, II and III
→ −
10. Request. An object experiences a net force F , causing it to accelerate with a magnitude a. If the same object experiences twice the net force, what is the new acceleration? A. a
B. 2a
C. 4a
D. 6a
E. 8a
11. I-push mo yan 2. A stockroom worker pushes an 11- kg mass on a horizontal surface with a constant speed of 3.5 m / s. The coefficient of kinetic friction between the box and the surface is 0.20. What horizontal force must the worker apply to maintain the motion? A. 12 N
B. 16 N
C. 18 N
D. 22 N
E. 28 N
12. Minecraft. A 500 .0 kg iron block can be accelerated on a frictionless plane at a constant rate from rest to 444.0 m/s in 1.800s. What was the magnitude of the net force on the block? A. 1.259 × 104 N
C. 1.233 × 105 N
B. 4.900 × 104 N
D. 2.220 × 105 N
A– 4
E. 3.996 × 105 N
Final Exam
First Semester, AY 2013–2014
Physics 71
13. Rough and banked. A car with mass m is traveling with speed v round a rough curve. The curve has a radius R and is banked at an angle β . Let the variables n and f denote the normal force and friction on the car. Which of the following is a correct expression of Newton’s 2nd law? A. f + n =
mv R
2
B. f + n sin β =
mv R
2
C. f cos β + n sin β =
mv R
2
D. f sin β + n cos β =
mv R
2
E. f + n cos β =
mv R
2
14. Slide. A block is at rest on top of an incline. The coefficient of static friction between the wedge and the block is µs = 0.450. At what angle of inclination, θ , would make a 10.0- kg box slide down the surface of the wedge? A. 0.00780◦
D. 65.8◦
B. 0.260◦ C. 24.2◦
E. 88.7◦
15. Final Motion. A stationary crate is pushed to the right along a frictionless floor by a force → − F of constant magnitude. After some time, another force equal in magnitude is applied → − collinear and opposite to F . Which of the following will be the final motion of the crate? A. It is at rest.
D. It is moving at constant speed.
B. It is slowing down.
E. It is accelerating.
C. It is speeding up. 16. Constant Circulation. Which of the following quantities is constant for an object in uniform circular motion? A. speed
D. radial acceleration
B. velocity
E. direction of motion
C. acceleration
A– 5
Final Exam
First Semester, AY 2013–2014
Physics 71
17. Man in the Stand. A person of mass 100. kg stands on top of a 100.-kg platform attached to a pulley system as shown. How much force is needed to pull the person up at a constant rate? A. 1.96 × 103 N
D. 654 N
B. 1.47 × 103 N C. 981 N
E. 490 N
18. Workisagift. A 4- N force is applied in the direction of motion of a moving object and then removed after the object has traveled an additional 5 m. What is the work done by this force? A. 12 J
B. 15 J
C. 18 J
D. 20 J
E. 30 J
19. Up and up. An object of mass M is resting on a platform at a height S 0 with respect to the ground. Its potential energy at that location is U 0 . If the platform was raised to a new height of 32 S 0 , what is the new potential energy of the object? A. zero
B. 12 U 0
C. U 0
20. Skyrim. A spherical baby dragon of mass m = 2.00kg is dropped from a height h onto a spring with spring constant k = 1.96 × 103 N/m as shown. Find h if the maximum distance of compression of the spring is 0.099m. A. 0.400m B. 0.490m C. 0.500m D. 0.900m E. 4.900m
A– 6
D. 32 U 0
E. 2U 0
Final Exam
First Semester, AY 2013–2014
Physics 71
21. Midway. A ball of mass m is thrown upwards from the ground at speed v . What is the gravitational potential energy of the ball midway between the ground and the maximum height the ball can reach? A. mv
B. 12 mv
C. mv 2
D. 12 mv 2
E. 14 mv 2
22. Sup-per flyieeeee! A typical adult house fly ( Musca domestica) has an average mass of 12.0 × 10−6 kg. What is the momentum of the fly if, for some reason, it became SUPER FLY and was able to travel at the speed of sound ( 340m/s)? A. 3.5 × 10−8 kg ·
m s
B. 4.1 × 10−3 kg ·
m s
C. 3.5 × 10−2 kg ·
m s
D. 4.1 × 10+3 kg ·
m s
E. 2.8 × 10+7 kg ·
m s
23. Collide. A 5.0- kg block collides with a 10.- kg block initially at rest. After the collision, the 5.0- kg block moves with a velocity 1.0 m / s to the left, while the other block moves with a velocity 5.0 m / s to the right. What is the speed of the 5.0- kg block before the collision? A. 4.5 ms
B. 45. ms
C. 9.0 ms
D. 90. ms
E. 7.0 ms
24. Witchy. Which of the following statement(s) is/are TRUE about momentum-impulse theorem? I. If there is a change in momentum, there is a net force that acts for a certain amount of time. II. If the change in momentum occurs over a shorter time, the force of impact is larger. III. If the change in momentum occurs over a longer time, the force of impact is smaller. A. I only
C. I and III only
B. I and II only
D. II and III only
A– 7
E. I, II and III
Final Exam
First Semester, AY 2013–2014
Physics 71
25. Stick-then-slip motion. The track shown in the figure is rough on the left ramp and smooth on the right ramp. A solid sphere rolls without slipping down the left ramp from a height h1 , and slides up the right ramp up to a height h2 . Which of the following gives the correct relationship between h1 and h2 ? A. h2 = 27 h1
D. h2 = 37 h1
B. h2 = 25 h1 C. h2 = 15 h1
E. h2 = 57 h1
26. Fan Stop. An electric fan’s blade is initially rotating at constant angular speed. If the power supply is turned off, it slows down at a rate of 1.0 rad . If it stops in 2.0 s, what is the s initial angular speed of the blade? 2
A. 0.25 rad s
C. 1.0 rad s
B. 0.50 rad s
D. 2.0 rad s
E. 4.0 rad s
27. The Moment of Inertia. A baton consists of two balls each with mass m but of negligible radius, connected by a rod of length L with a negligible mass. What is the moment of inertia of the baton about an axis perpendicular and passing through the center of the rod? A. 14 mL2
B. 12 mL2
C. mL2
28. I miss I. Wheel B with rotational inertia I , is rotating with angular speed ω0 about an axis perpendicular to the wheel and passing through its center. A nonrotating wheel A with rotational inertia 2I is suddenly dropped onto wheel B as shown. What will be the angular speed of the system of two wheels?
ω0 4 ω0 B. 3
A.
C.
ω0 2
E. 3ω0
D. 2ω0
A– 8
D. 2mL2
E. 4mL2
Final Exam
First Semester, AY 2013–2014
Physics 71
29. I turn to you. A turn table ( I cm = 10. kg · m2 ) is pushed on the edge to turn at a rate of 2.0 rad . What is the magnitude of the net torque acting on the turn table? s 2
A. 5.0 N · m
C. 10. N · m
B. 8.0 N · m
D. 12 N · m
E. 20. N · m
30. Reach the Top. Initially, a solid uniform ball rolls without slipping horizontally with a translational speed of 5.00 m / s. It then moves up along a rough ramp. What is the maximum height h that the ball could reach before it goes back down the ramp? A. 0.255 m
C. 1.27 m
B. 0.357 m
D. 1.78 m
E. 2.55 m
31. Lastikman!!! When Lastikman deformed his body, he felt 2.0 Pa of stress and 4.0 of strain. What is his elastic modulus? A. 0.25 Pa
C. 0.75 Pa
B. 0.50 Pa
D. 1.0 Pa
E. 2.0 Pa
32. Kepler. Which of the following statements regarding Kepler’s Laws is/are TRUE? I. Planets move in elliptical orbits with the sun in one of the foci of the ellipse. II. The periods of planets are proportional to the square of the major axis lengths of their orbits. III. A line from the sun to a given planet sweeps equal areas in equal times. A. I
C. III only
B. II
D. I and III only
E. I, II and III
33. He/She. What is the magnitude of the gravitational force between a 60- kg girl and a 70- kg boy who are standing 2.0 m apart A. 5 × 10−8 N
C. 7 × 10−8 N
B. 6 × 10−8 N
D. 8 × 10−8 N
A– 9
E. 9 × 10−8 N
Final Exam
First Semester, AY 2013–2014
Physics 71
34. Saturn. The planet Saturn has about 100 times the mass of the Earth and is about 10 times farther from the Sun than the Earth. Compared to the gravitational force experienced by the Earth due to the Sun, how great is the gravitational force experience by Saturn due to the Sun? A. 100 times as great
D. 1/10 times as great
B. 10 times as great
E. 1/100 times as great
C. The same 35. SHM-ninja. An object of mass m , oscillating on the end of a spring with spring constant k , has an amplitude A. What is the maximum speed of the object?
k A. A m B. A
C. A
m k
k
m k D. A2 m
E. A2
m k
36. Flow. Consider an incompressible fluid flowing through a horizontal pipe. Which of the following statement(s) is/are TRUE if the cross-sectional area of the pipe is decreased? I. speed of the fluid increases II. volume flow rate of the fluid increases III. fluid density decreases A. I only
C. III only
B. II only
D. I and II only
E. I, II and III
37. Buoyant force. Two objects of the same mass are floating in a bowl filled with fluid. Object A is denser than object B. Which of the following statement is ALWAYS TRUE ? A. Buoyant force is greater on A than on B. B. Buoyant force is greater on B than on A. C. Buoyant force is the same for both objects. D. Buoyant force does not depend on the density of fluid. E. The volume of A is greater than the volume of B.
A – 10
Final Exam
First Semester, AY 2013–2014
Physics 71
38. Scuba Steve. Steve is scuba-diving in the Pacific ocean, carrying a barometer. At depth h1 from the surface, he measured the pressure as P 1 . When he went deeper to h2 , the pressure increased to P 2 . What is the pressure at the midway depth: ( h1 + h2 )/2? A. P 1 + P 2
C. P 2 − P 1
B. (P 1 + P 2 )/2
D. (P 1 − P 2 )/2
E. (P 2 − P 1 )/2
39. Waves are Fun. Which of the following is ALWAYS TRUE for a mechanical wave? A. travels within some medium B. travels in a periodic motion C. transports matter D. only happens on a string E. travels perpendicular to the disturbance in a medium 40. Lengthy. A string tied at both ends oscillates in the fundamental frequency. If it is made to oscillate in its third harmonics, by what factor will the wavelength change? A.
1 9
B.
1 3
C.
2 3
D. 3
E. 9
41. Magneto the Loner. When Magneto used to play alone as a child, he would tie a rope to a tree to make sure that the rope is fixed. Then, he would use the rope to create a wave. When the wave reaches the tree and gets reflected, how will the reflected wave travel? A. away from the tree, not inverted B. away from the tree, inverted C. towards the tree, not inverted D. towards the tree, inverted E. it will uproot the tree 42. Mulawin. On the planet Mulawin, a male ornithoid is flying toward his stationary partner at 25 .0 m/s while singing at a frequency of 1 .20 kHz. If the stationary partner hears a tone of 1.24kHz, what is the speed of sound in the atmosphere of Mulawin? A. 344 m/s
C. 621 m/s
B. 549 m/s
D. 682 m/s
A – 11
E. 775 m/s
