University of the Philippines College of Science
Physics 71
Set A First Long Exam First Semester, AY 2015–2016
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First Long Exam
First Semester, AY 2015–2016
Physics 71
Instructions: Choose the letter of the best answer to each of the following questions. Use Mongol 2 pencil only to shade your answer to the exam. To change your answer, erase neatly your old answer and simply shade the new one. Any form of cheating in examinations or any act of dishonesty in relation to studies, such as plagiarism, shall be subject to disciplinary action. Following instructions is part of the examination.
1. Pag-ikot ng mundo. Earth is moving about 1.00 × 105 [km/h] relative to the sun. How much did the earth moved in 1 [week]? Easy A. 2.40 × 106 [km] B. 1.68 × 106 [km]
C. 2.40 × 107 [km]
0.64% 4.47%
D. 1.68 × 107 [km]
0.96% 93.93%
2. Mula dito hanggang duon. A dog is initially located at position (1 .0[m], 2.0 [m]) of the map. The dog then run directly towards (3.0[m], 2.0[m]) before ending in (3.0[m], 4.0[m]). What is the total distance traveled by the dog? Average A. 7.0[m]
B. 4.0[m] C. 2.8[m] D. 2.0[m] 2.24% 73.80% 19.49% 4.47% 3. Back to headquarters. Joy is looking for a way back to headquarters. From her initial position, headquarters is 3.0[km] directly north. She then decides to walk 1.0[km] eastward. What is the location of headquarters with respect to her new position? Average A. 18 North of West 7.67%
C. 18 East of North 15.97%
B. 72 North of West 68.05%
D. 72 East of North
◦
◦
◦
◦
8.31%
4. Jetsetter. A private jet takes-off from the hangar. First, it flies 61.0[km] East, and then it turns and travels 113 [km], 15 North of West. Where is the jet located relative to the hangar? Easy ◦
A. 31.8 [km] East, 109 [km] North 7.35%
C. 90.2[km] West, 109 [km] South 3.19%
B. 170 [km] East, 29.2[km] South 8.95%
D. 48.1[km] West, 29.2 [km] North 80.51%
5. C. The speed of a robot as a function of time is expressed as
v (t) = 0.02[m/s] + 2Ct2. If t has a unit of seconds, what is the unit of C ? Easy A. [m · s]
4.79%
B. [m/s]
3.19% A– 2
C. [m/s2 ] 8.31%
D. [m/s3 ] 83.71%
First Long Exam
First Semester, AY 2015–2016
Physics 71
6. Malling. It took Molly an hour to walk to the mall from her house and back. The distance from her house to the mall is 4 [km]. Which of the following statements is FALSE? Easy A. Displacement is zero. 2.88% 92.01% B. Distance is zero.
velocity is zero. 1.92% C. Average 3.19% D. Speed is 8 [km/hr].
7. Motion sensor eye. At t = 0, the velocity of your classmate is +2.00[m/s] with zero acceleration. You noticed that at t = 5.00[s], your classmate’s instantaneous velocity and acceleration are now +10.0 [m/s] and +2.00[m/s2 ], respectively. What is your classmate’s average acceleration from t = 0 to t = 5.00[s]? Average A. +0.40[m/s2 ] 16.61% B. +1.00[m/s2 ] 8.63%
C. +1.60[m/s2 ] D. +2.40[m/s2 ]
68.69% 6.07%
8. Sssss. A snake moves along x-direction as described by x(t) = 2.0 [m/s2 ]t2 + 4.0[m]. What is its instantaneous speed at t = 4.0[s]? Average A. 4.0 [m/s] 5.11%
B. 8.0 [m/s] 21.09%
C. 12[m/s] 4.15%
D. 16[m/s]
A. 2.00 [m] 5.75%
B. 4.00[m] 44.41%
C. 6.00[m] 16.61%
D. 8.00[m] 32.91%
69.33% 9. 2nd Second. At t = 0, the car starts from rest and accelerates at a constant rate in a straight line. At t = 1.00[s], the car covers a distance of 2.00[m]. How much distance will the car cover after t = 2.00 [s]? Difficult
10. Trese. Trese starts from rest and begins accelerating at the constant rate of 5.00[m/s2 ]. How much time will it take for her to travel 500. [m]? Easy A. 5.80 [s] 0.96%
B. 14.1[s] C. 23.8[s] D. 54.5[s] 3.83% 2.24% 92.97% 11. Prepol. A ball is thrown upward and is in free fall. Which of the following best describes the ball’s velocity on its way down after reaching the highest position? Easy A. Downward and increasing in magnitude
85.94% 9.27% B. Downward and decreasing in magnitude C. Downward and remains the same
D. Upward and accelerating
A– 3
4.47% 0.32%
First Long Exam
First Semester, AY 2015–2016
Physics 71
For the next two items, consider the plot of the velocity of the car as a function of time (solid line) shown in the figure below.
12. Kalye serye. What is the average acceleration of the car in the time interval t = 1.0[s] to t = 2.0[s]? Easy A. 0.50[m/s2 ] 0.96%
B. 2.5 [m/s2 ] 10.22%
C. 3.0 [m/s2 ] 7.99%
D. 5.0 [m/s2 ] 80.83%
13. The race. What is the instantaneous acceleration of the car at t = 1.0[s]? Difficult A. 0.50[m/s2 ] 33.23%
B. 2.5 [m/s2 ] 13.42%
C. 3.0 [m/s2 ] D. 5.0 [m/s2 ] 8.31% 43.45% 14. Kinematic. Which of the following kinematic equations describe(s) the motion of a ball vertically thrown upward from the ground with a speed of 2.00[m/s]? Set the initial position to be at the origin, and upward direction as positive. Easy I. vy = 2.00[m/s] − 9.81[m/s2 ]t
III. vy = 2.00[m/s] + 9.81[m/s2 ]t
II. y = 2.00[m/s]t − 4.90[m/s2 ]t2
IV. y = 2.00[m/s]t + 4.90[m/s2 ]t2
84.98% B. I and III only 4.15%
A. I and II only
C. II and IV only 1.28% D. III and IV only 9.27%
A– 4
First Long Exam
First Semester, AY 2015–2016
Physics 71
15. AlDub. Yaya Dub jumped off a roof with an initial upward velocity of 2 .00[m/s] and is falling towards Alden who is 5 .00 [m] below. What is the speed of Yaya Dub just before Alden catches her? Easy A. 9.01[m/s] 1.28%
B. 9.06[m/s] 9.90%
C. 10.1 [m/s] 81.79%
D. 10.6 [m/s] 5.75%
16. Fly. The position function of the fly is written as r(t)
= 3.00[m/s3 ]t3 ˆı + (1.00[m] − 2.50[m/s]t) . ˆ
What is the average velocity of the fly from t = 0 to t = 4.00 s? Average
48.0 [m/s] ˆı + 2 .50[m/s] ˆ 1.60% B. −192 [m/s] ˆı + 10.0 [m/s] ˆ 1.60%
A.
−
C. +48.0 [m/s] ˆı − 2.50[m/s] ˆ 68.05% D. +192 [m/s] ˆı − 10.0 [m/s] ˆ
27.80%
17. Point P. Consider the figure on the right. If the value of the angle is θ = 30.0 , what is the position of point P in vector representation if the vector starts from the origin? Easy ◦
ı + 5.20 [m] ˆ 4.15% A. +3.00 [m] ˆ ı + 3.00 [m] ˆ 95.85% B. +5.20 [m] ˆ C.
−
3.00 [m] ˆı − 5.20[m] ˆ 0%
D.
−
5.20 [m] ˆı − 3.00[m] ˆ 0%
18. projectile runway . A projectile is launched at an angle θ above the horizontal. Ignoring air resistance, at what point in the projectile’s trajectory is the speed lowest? Easy 92.01%
1.60%
3.51% 2.88%
A– 5
First Long Exam
First Semester, AY 2015–2016
Physics 71
19. Bolahan. A boy hits a football so that the ball leaves the ground at point (0, 0) with a velocity of 25.0 [m/s], 40.0 above the ground. What is the horizontal and the vertical position (x, y ) of the ball after 2.00[s]? Average ◦
A. (38.3[m], 12.5[m]) 59.11% B. (18.7[m], 38.3[m]) 3.19%
C. (18.7[m], 19.6[m]) 3.83% D. (38.3[m], 32.1[m]) 33.55%
20. From the edge. A small box slides off a horizontal table at a speed of v and strikes the floor after some time. How high is the table if the box is found at some distance x from the edge of the leg of the table? Average
g x A. 2 v B.
2
x 2g v
2
52.40%
C.
2
g 2x 2 v g x
2
18.85%
D.
2 2v
21.41% 6.39%
21. Ikot-ikot lang. Which of the following statements is TRUE about circular motion? Average A. An object moving in a uniform circular motion has radial and tangential compo29.07% nents of acceleration. B. An object moving in uniform circular motion has zero acceleration. 3.83% C. An object moving in non-uniform circular motion has atan = 0. D. An object moving in uniform circular motion has constant speed.
4.15% 62.94%
22. Loop the loop. A skater moves in the 10 .0[m] diameter loop. What is the skater’s radial acceleration if the skater moves in a constant speed of 8.00[m/s]? Average A. 1.60[m/s2 ] 4.15%
B. 6.40[m/s2 ] 16.93%
C. 12.8 [m/s2 ] 78.27%
D. 25.6 [m/s2 ] 0.64%
23. Perpendicular. A particle’s motion in x-y plane is described by a velocity and acceleration vector in such a way that the acceleration has some component parallel and perpendicular to the velocity vector. What does the perpendicular component of acceleration do to the velocity vector of the particle? Average A. Decreases the speed
3.51%
B. Changes the direction 67.41%
A– 6
C. Increases the speed 3.83% 24.92% D. Both A and B
First Long Exam
First Semester, AY 2015–2016
Physics 71
24. Boat On The River. A boat is traveling to the East at 10 . [m/s] with respect to the water of a river. The water is flowing at 5.0 [m/s] to the West with respect to the ground. What is the boats velocity with respect to the ground? Easy A. 15[m/s] East
C. 5.0 [m/s] East
81.15% 1.60% D. 5.0 [m/s] West
16.61% 0.64% B. 15[m/s] West
25. Like a Virgin. Which of the following systems in an inertial reference frame has/have a zero net force? Average I. A train moving in a straight path at the constant speed of 4.00[m/s]. II. A stone moving in a circular path at the constant speed of 2.00[m/s]. III. A box moving in a straight path at the increasing speed with a rate of 2.00[m/s2 ]. A. I only
C. I and II only 32.91%
57.19% B. II only 7.35%
D. I and III only 2.56%
26. Contact-kin lang si Force. Which of the following is/are contact force/s? Average I. Normal Force A. I only B. II only
II. Tensile Force
19.49% 8.95%
III. Gravity C. III only
3.51%
D. I and II only
67.73%
27. Shahara’s minion. Shahara is observing her minion on top of a block that slides with constant speed along a straight line. If Shahara is at rest, which of the following is ALWAYS TRUE? Average A. No force is acting on the minion.
4.47%
B. A constant non-zero net force acts on the minion. 25.88% 62.30% C. A zero net force acts on the minion. D. The net force acting on Shahara is opposite the direction of minion’s motion. 7.03% 28. Lonesome Lemon. A lemon is placed on top of a flat table. Which of the following forces comprise an action-reaction pair? Average B. The weight of the lemon and the weight of the table
37.70% 2.24%
C. The weight of the lemon and the force of the lemon on earth
54.63%
A. The weight of the lemon and the normal force on the lemon
D. The force of the table on the lemon and the normal force on the lemon 5.11% A– 7
First Long Exam
First Semester, AY 2015–2016
Physics 71
29. Love aPair. A pair of wooden boxes A and B are arranged in a frictionless table as shown in the figure below. A force F is applied on box A and the two boxes start to move. What is the direction of the normal force acting on box A due to box B? Average A. to the right 5.43%
B. to the left 75.72%
C. upward 17.89%
D. downward 0.96%
30. Sliding block. A block is fired up from a rough ramp with an incline angle of 35 . Which free-body diagram properly represents the forces acting on the block? Difficult ◦
B is the correct answer
2.56%
40.26%
55.59%
1.60%
31. Fast and the Curious. Dom’s car enters a horizontal, curved roadbed of radius 73 .4[m]. The coefficient of static friction between the tires and the roadbed is 0.20. What is the maximum speed with which the car can safely negotiate the unbanked curve? Average A. 10.7 [m/s] 6.39%
B. 12.0 [m/s] 62.30%
C. 26.8 [m/s] 22.68%
D. 60.0 [m/s] 7.99%
32. PabebeOnIce. The two Pabebe Girls with masses m1 and m2 went ice skating. They are both initially at rest then pushed each other. If m1 > m2 , which of the following statements is TRUE about the girl’s motion while being pushed? Average
7.03%
A. Pabebe Girl 1 accelerates faster than Pabebe Girl 2.
76.36%
B. Pabebe Girl 2 accelerates faster than Pabebe Girl 1.
14.70%
C. Their accelerations are equal since they experienced the same magnitude of force. A– 8
First Long Exam
1.60%
First Semester, AY 2015–2016
Physics 71
D. Both do not accelerate since they are moving with constant speed.
33. Pusher. A block of wood is resting on a horizontal rough floor. If you continuously pushed the block with a constant force equal to the static frictional force, what will happen to the block? Average
68.05% A. It will not move. 17.25% B. It will move with constant non zero velocity. 8.31% C. It will move with constant non zero acceleration. 6.39% D. It will move but will stop eventually. 34. Question with no tension. A pendulum bob moves in a horizontal circle such that the string makes an angle of 30 about the vertical. If the radius of the horizontal circle is 0.30[m], what is the tangential speed of the bob? Difficult ◦
A. 1.3 [m/s] 37.06%
C. 2.3 [m/s] 22.04%
B. 1.6 [m/s] 30.99%
D. 2.9 [m/s]
9.90%
35. Blocks. Block A (mA = 3.0[kg]) is on the verge of motion on a tabletop. It is connected by a horizontal cord passing over a light, frictionless pulley to a hanging block B ( mB = 1.5[kg]). The coefficient of kinetic friction between block A and the tabletop is 0.20 and the blocks were released from rest. What is the speed of each block after it moved 0.030 [m]? Average A. 0.050[m/s] 11.82% 16.29% B. 0.11[m/s]
C. 0.34[m/s]
D. 1.8 [m/s]
36. ecStatic. A 1 .00[N] ball, suspended from the ceiling by massless wires, is in static equilibrium as shown in the figure. What is the magnitude of the tensional force T 1 ? Average A. 0.732 [N] 53.04% B. 0.897 [N]
23.96%
C. 2.73 [N] 17.89% D. 3.35 [N]
A– 9
4.47%
58.15% 13.42%
First Long Exam
First Semester, AY 2015–2016
Physics 71
37. Repose. A 25.0 [kg] box of textbooks is initially at rest on a rough ramp that makes an angle α with the horizontal. The coefficients of kinetic and static friction between the box and the ramp are 0 .500 and 0.700, respectively. What the minimum angle α at which the box starts to slip? Difficult A. 26.6 24.60%
B. 35.0
◦
◦
C. 30.0 12.14% ◦
49.52%
D. 44.4 12.78% ◦
38. Slide. A group of students with total mass of 200 [kg] ride on a sled while sliding down an incline with angle α. The coefficient of kinetic friction between the sled and the incline is 0.300. At what angle will the sled slide down with constant velocity? Average A. 12.3
◦
B. 16.7
◦
2.24%
C. 17.5 27.16%
60.38%
D. 72.5
◦
◦
9.58%
39. Rock not roll to the World! A 5.0[kg] rock, initially at rest slides from the top of the frictionless inclined plane. What is its Average speed after 1.0[s]? A. 9.8 [m/s] 21.41% B. 7.5 [m/s]
50.48%
C. 6.3 [m/s]
23.96%
D. 0.64[m/s]
4.15%
40. Sa tamang panahon. At t = 0, a box with mass of 45 [kg] is initially moving at constant velocity of 1.0 [m/s] to the right. The box is then pushed by a force of magnitude 360 [N] to the right such that it slides on a rough floor with coefficient of kinetic friction µk = 0.55. At what time will the box acquire a velocity of 6.0 [m/s] to the right? Average A. 0.62 [s] 14.70%
B. 0.93[s] 10.54%
A – 10
C. 1.2[s] 15.97%
D. 1.9[s] 58.15%
