p6 71 samplex

University of the PhilippinesCollege of Science

Physics 71

Set AFirst Long Exam

Second Semester, AY 2013–2014

Name: Instructor:

Section/Class Schedule: Student Number:

Course: College:

First Long Exam Second Semester, AY 2013–2014 Physics 71

Instruction: Choose the letter of the best answer to each of the following questions.To changeyour answer, cross (X) out your original answer and supply your new answer with your signa-ture beside the item. Use g = 9.81m/s2. Ignore air friction unless otherwise stated. Any formof academic dishonesty in relation to studies shall be subject to disciplinary actions.

1. Arrows. Consider three vectors, K, L, and M of equalmagnitudes as shown in the figure. Which of the follow-ing is/are true?

A. K+ L = M

B. L+M = K

C. M+K = L

D. Choices A, B and C are all true

E. Choices A, B and C are all false

2. Magnitude. Consider two vectors A = 5i+ 4j− 2k and B = −3i− 2j+ 6k. What is themagnitude of the vector sum A+B?

A. 2√3 B. 2

√6 C. 2

√5 D. 6

√2 E. 3

√2

3. PJB. Given two vectors P = −2i− 3j and J = 4i+ 7j What is the magnitude of P · J?

A. zero B. 2√5 C. 9 D. 26 E. 29

4. Dimension Mania. The total mechanical energy is defined as E = mgh+ 12mv

2 where Estands for energy, m is the mass, g is the acceleration due to gravity, h is the height, andv is the speed. If all the quantities are in SI units, which of the following is the unit forenergy?

A. [kg][m]

[s]2

B. [kg][m]2

[s]

C. [kg][m]2

[s]2

D. [kg][m]

[s]

E. [kg]12[m]

[s]3

5. PSP vs. GBA. A 0.20- kg PlayStation Portable (PSP) and a 0.10- kg Game Boy Advance(GBA) fall freely from rest from a height of 25.0m. What is the ratio of the PSP’s speedto the GBA’s speed after they fall for 2.0 s?

A – 2


A. 1 : 2 B. 2 : 1 C. 1 : 1 D. 4 : 1 E. 1 : 4

6. Fast and furious. At time t = 0, a police cruiser is at x = 0 and the policemen insidesee a stolen car at x = −50.0m. The thieves are driving the car at a constant velocity of50.0m/s i. The police cruiser starts accelerating from rest at a constant rate of 4.76m/s2 i.What will be the speed of the cruiser when it starts overtaking the stolen car?

A. 4.76m/s

B. 5.01m/s

C. 50.0m/s

D. 95.0m/s

E. 100.m/s

7. Start me up. How long will it take to accelerate an object from rest to 22.0m/s along astraight line if the magnitude of the acceleration is 2.20m/s2?

A. 0.10 s B. 4.84 s C. 10.0 s D. 48.4 s E. 100. s

8. Two Directions. A car is accelerating at 1.0m/s2 on a straight highway. Initially, the carhas a speed of 5.0m/s. After 9.0 s, the car is now moving with speed 4.0m/s. What is theaverage acceleration of the car for this time interval?

A. 1.0m/s2

B. 1.1m/s2C. 0.11m/s2

D. 0.44m/s2E. 0.55m/s2

9. Phlanking of P71. You drop a ball from a height h and it reaches the ground after sometime t. If you decrease the height to h/2, how long will the ball take to reach the ground?

A. t B. 2t C.√2t D. t/2 E. t/

√2

10. Bulkan. A large boulder is ejected vertically upward from a volcano with an initialspeed of 40.0m/s. At what time after being ejected is the boulder moving at 20.0m/s up-ward?

A. 1.88 s B. 2.04 s C. 3.12 s D. 4.06 s E. 4.18 s

11. Launch break. A ball is thrown straight upwards. At 3.00m above its launch point, theball’s speed is one-half its launch speed. What maximum height above its launch pointdoes the ball attain?

A. 5.50mB. 5.00m

C. 4.50mD. 4.00m

E. 3.50m

A – 3


12. Pepito. Pepito runs 150m to the left at an average speed of 2.0m/s, then he runs 80.m tothe right at an average speed of 4.0m/s. What is the magnitude of his average velocity forthe entire trip?

A. 0.42m/s

B. 0.74m/s

C. 0.92m/s

D. 1.12m/s

E. 2.42m/s

13. RAC. A car travels on a horizontal road. Its position, x, as a function of time, t, is givenby x(t) = 5.0m/s2 t2 − 380m. What is the acceleration of the car after t = 3.0 s?

A. zeroB. 5.0m/s2

C. 10.m/s2

D. 380m/s2E. 42m/s2

14. This is Sparta! King Leonidas throws a rock at an angle of 60.0◦ from the horizontal. Ifits initial horizontal velocity is 30.0m/s, what is its initial vertical velocity?

A. 17.3m/s

B. 30.0m/s

C. 52.0m/s

D. 60.0m/s

E. 104.m/s

15. Pokemon X and Y. Pokemon Xerneas is traveling North at 5.0m/s and directly behind it,Pokemon Yvetal is traveling South at 3.0m/s. What is the velocity of Yvetal relative toXerneas?

A. 2.0m/s, NorthB. 2.0m/s, South

C. 4.0m/s, SouthD. 8.0m/s, North

E. 8.0m/s, South

16. Turo-turo. A particle started to move with a velocity −→v0 under a constant acceleration −→aas shown. After 20.0 s, where will the particle’s final velocity be directed?

A – 4


17. Speed. At which point in the projectile’s trajectory is the speed smallest?

18. Earth-worm. Planet Earth (RE = 6.38 × 106m) is ro-tating with a period of T = 1day about its axis. Whatis the radial acceleration of an earthworm located alongthe Earth’s equator?

A. 5.4× 10−3m/s2

B. 3.4× 10−2m/s2

C. 3.0× 101m/s2

D. 9.3× 102m/s2

E. 2.9× 103m/s2

19. Runner. A guy runs around a circular track with radius 300.m at a constant speed in15.0min. What is the magnitude of his radial acceleration?

A. 0.0146m/s2

B. 1.33m/s2C. 2.09m/s2

D. 52.6m/s2E. 790.m/s2

20. Horizontal Drop. An object is launched horizontally from the top of a 200.m buildingwith an initial speed of 15.0m/s. What is the object’s speed just before it hits the ground?

A. 34.7m/s

B. 41.7m/s

C. 46.8m/s

D. 60.8m/s

E. 64.4m/s

21. Balloon rises. You throw a water-filled balloon at 45◦ above the horizontal with a speedof 12.m/s. What maximum height will the water-filled balloon reach?

A. 86 cmB. 370 cm

C. 520 cmD. 730 cm

E. 1500 cm

A – 5


22. Wreck it, Tin! A girl launches three objects simultane-ously into the air. Objects A, B, and C leave the girl’shand at different angles, 60◦, 45◦, 30◦ respectively. Thetrajectories followed by the objects are shown. Whichobject/s hit/s the ground first?

A. Only object A and Object C at thesame time.

B. All three hit the ground at the sametime.

C. Object A

D. Object B

E. Object C

23. Hulog ng langit. An airplane is flying with a velocity of 90.0m/s at an angle of 23.0◦ abovethe horizontal. When the plane is 114m directly above a dog standing on a level ground, asuitcase drops out of a luggage compartment. How far from the dog will the suitcase land?

A. 512m B. 692m C. 713m D. 795m E. 822m

24. Flight of the Bullet. After a bullet is fired into frictionless space, how much force is neededto maintain its motion?

A. Twice the force with which it was fired.

B. The same amount of force with which it was fired.

C. One half of the force with which it was fired.

D. The amount will depend on its current velocity.

E. Zero, since no force is necessary to keep it moving.

25. Inertial Transit. On which of the following situations can a bus be an inertial frame ofreference?

A. when it is rounding a curve at con-stant speed

B. when it is slowing down up a hillC. when it is speeding up down a hill

D. when it is falling towards a lake

E. When it is sinking straight downthe lake at constant speed

26. Mang Juan at Planet Di. Mang Juan’s weight on Earth is 637N. What will be his mass

on Planet Di if the acceleration due to gravity near the surface is gDi =1

8gEarth?

A – 6


A. 3.30× 101 kg

B. 6.49× 101 kg

C. 1.10× 102 kg

D. 2.60× 103 kg

E. 5.10× 103 kg

27. Epol, apol. An apple is placed on a plate, which rests on top of a table. Which of thefollowing forces is the reaction to the apple’s weight?

A. push of plate on appleB. push of table on plateC. push of table on apple

D. pull of apple on Earth

E. pull of Earth on apple

28. LQG. A block slides completely through a vertical circular track (loop-the-loop). Whichdiagram shows the net force on the block at different parts of the track? Ignore frictionfrom the track.

A.

B.

C.

D.

E.

29. The Force Horsemen. A 3.00 kg object hangs at an an-gle θ = 30.0◦ while given a force F as shown in thefigure. If the tension on the rope is 20.0N, what is themagnitude of the force, F ?

A. 15.7N

B. 22.1N

C. 26.0N

D. 36.8N

E. 49.4N

30. Tulak tulak din. You continuously exert a constant horizontal force of 120N to a tableon a frictionless surface thus obtaining a speed of 5.0m/s from rest for a distance of 10.m.What is the mass of the table?

A. 75 kg B. 110 kg C. 120 kg D. 96 kg E. 80. kg

A – 7


31. The Block. A 20.0 kg block is resting on a horizontal floor. The coefficient of static frictionbetween the block and the floor is 0.400. If a force F = +20.0Ni is applied on the block,what is the resulting frictional force acting on the block?

A. zero

B. +20.0Ni

C. −20.0NiD. +78.5Ni

E. −78.5Ni

32. Push Mo Yan! A 200N box is moving at a constant speed along a flat horizontal surfacewhile being pushed by a horizontal force. If the coefficient of kinetic friction between thebox and ground is 0.5, what is the magnitude of the frictional force?

A. 50N B. 100N C. 200N D. 300N E. 400N

33. Just right. An object of mass M is pushed up a friction-less incline as shown in the figure. What is the magni-tude of the horizontal force F needed to allow the objectto slide up the incline with constant velocity?

A. Mg

B. Mg sin θ

C. Mg cos θ

D. Mg tan θ

E. Mg cot θ

34. Tense string. A 1.0 kg mass tied to the end of a string 0.50m is made to rotate in a verticalcircle. At the lowest point of the circular path, the speed of the point mass is 3.0m/s. Whatis the tension on the string at this point?

A. 8.2N B. 16N C. 19N D. 28N E. 46N

35. When the goin’ gets rough. A horizontal force of magnitude 50.0.N is needed to give a10.0 kg box an acceleration of 1.45m/s2 on a rough and horizontal surface. What is thecoefficient of kinetic friction between the box and the floor?

A. 0.148 B. 0.362 C. 0.408 D. 0.510 E. 0.658

36. Av-Rock. When you push a box with a horizontal force of magnitude 4.0N on a roughlevel surface, it moves with an acceleration of magnitude 2.0m/s2. If you push the samebox with a horizontal force of magnitude 8.0N, it moves with an acceleration of magnitude6.0m/s2. What is the mass of the box?

A – 8


A. 2.0 kg B. 1.0 kg C. 1.3 kg D. 1.7 kg E. 3.3 kg

37. Tension. A 10−kg cube is suspended from a system ofcords, as shown in the figure. What is the tension in thehorizontal cord?

A. 10N

B. 50N

C. 70N

D. 100N

E. 200N

38. Speed Racer. A race car with mass m = 900 kg goes through a circular part of an un-banked track with radius of curvature R = 300m. If the coefficient of static frictionbetween the tires and road is µs = 0.5, what is the maximum speed at which the racer cantake the curve without sliding?

A. 4410m/s

B. 66.4m/s

C. 1150m/s

D. 38.4m/s

E. 1470m/s

39. Don’t think. A large box is twice as heavy as that of a medium box. Suppose both expe-rience the same net force. If the acceleration of the large box is a, what is the accelerationof the medium box?

A. a/√2 B. a/2 C. a D. 2a E.

√2a

40. Alin? Which of the following statements is/are TRUE about frictional force?

I. Fk and N are always perpendicular to each other.

II. In coefficients of friction; µs < µk.

III. Objects on smoother surfaces have larger coefficients of friction.

A. I onlyB. II only

C. III onlyD. I and II only

E. II and III only

41. Title. If you push horizontally with a force of +50N on a crate on a horizontal surface andmake it slide at constant velocity, how much frictional force acts on the crate?

A. zeroB. less than −50NC. −50N

D. more than +50N

E. +50N

A – 9


42. Equilibrium. A 5.0N box is to slide on a frictionless plane inclined 30.◦ above the hor-izontal. What force parallel to the plane is required to keep the box sliding at a constantspeed?

A. 0.50N B. 1.8N C. 2.2N D. 2.5N E. 2.8N

A – 10

p6 71 samplex

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launch speed

theballs speed

gbas speed

stolen car

magnitude of p j

time t

height h

maximum height