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Page 1 of 9
(21 problems)
Physics 101. / Hour Exam 2 / Summer 2015Exam Grading Policy—
The exam is worth a total of 106 points, and is composed of three types of questions.
MC5: multiple-choice-five-answer questions, each worth 6 points.
Partial credit will be granted as follows.
(a) If you mark only one answer and it is the correct answer,
you earn 6 points.
(b) If you mark two answers, one of which is the correct answer,
you earn 3 points.
(c) If you mark three answers, one of which is the correct answer,
you earn 2 points.
(d) If you mark no answers, or more than three, you earn 0 points.
MC3: multiple-choice-three-answer questions, each worth 3 points.
No partial credit.
(a) If you mark only one answer and it is the correct answer,
you earn 3 points.
(b) If you mark a wrong answer or no answers, you earn 0 points.
TF: true-false questions, each worth 2 points.
No partial credit.
(a) If you mark only one answer and it is the correct answer,
you earn 2 points.
(b) If you mark the wrong answer or neither answer, you earn 0 points.
Two masses are hung over a massless pulley as shown. The left mass is m1 = 5 kg and the right mass is m2 = 2 kg. Both masses begin h = 2.3 m off the ground. Initially both blocks are at rest.
1. After the blocks are released and begin to accelerate, how does the tension in the string compare with each of the weights of the blocks?
(A) T = W1 and T = W2
(B) T < W1 and T > W2
(C) T > W1 and T < W2
(D) T > W1 and T > W2
(E) T < W1 and T < W2
2. When the system is released, what is the magnitude of the acceleration of the right block?
(A) 1.7 m/s2
(B) 2.5 m/s2
(C) 4.2 m/s2
(D) 7.3 m/s2
(E) 9.8 m/s2
3. When the system is released, what is the tension in the string?
(A) 16 N
(B) 19 N
(C) 21 N
(D) 26 N
(E) 28 N
4. How fast is the left block moving right before it hits the ground?
(A) 1.5 m/s
(B) 2.1 m/s
(C) 3.7 m/s
(D) 4.4 m/s
(E) 5.1 m/s
This and the next problem are about the following situation:
5. A wheel with a radius of 0.2 m is initially at rest and undergoes an angular acceleration of a = 4 rad/sec2 for 20 seconds, after 20 seconds it continues to rotate at a constant angular velocity. What is the final speed of a point on the outer rim of the wheel?
(A) 7.5 m/s
(B) 11 m/s
(C) 16 m/s
(D) 23 m/s
(E) 29 m/s
6. How long, from rest, does it take for the wheel to travel through 250 revolutions?
(A) 17.3 s
(B) 21.1 s
(C) 22.8 s
(D) 25.3 s
(E) 29.6 s
7. A block of mass M = 2kg and velocity V = 5 m/s is moving on a horizontal frictionless surface. The block collides and sticks together with another identical block of M = 2kg initially at rest. Those two blocks collide and stick together with a third identical block initially at rest and all three blocks collide with and stick to a fourth identical block initially at rest. What is the final momentum of all four blocks?
(A) 2 kg*m/s
(B) 5 kg*m/s
(C) 10 kg*m/s
8. A bomb is initially at rest when it suddenly explodes into three pieces. A 5-kg piece goes north at 3 m/s, and a 2-kg piece goes east at 10 m/s. The speed of the third piece is 5 m/s. What was the initial mass of the bomb?
(A) 9 kg
(B) 10 kg
(C) 12 kg
(D) 14 kg
(E) 15 kg
9. Block 1 of mass M1=10 kg initially has a velocity of 20 m/s in the +x direction. It collides with Block 2 of mass M2=15 kg, which initially has a velocity of 10 m/s in the +y direction. The two blocks stick together after the collision. What is speed of the combined block after the collision?
(A) 10.0 m/s
(B) 12.7 m/s
(C) 15.5 m/s
(D) 18.6 m/s
(E) 19.0 m/s
The next three questions are about the following situation:
A constant force, F, is applied to two different blocks. One block has twice as much mass as the other block. The force is applied on each block for 10sec. Both blocks are at rest before the force acts on them.
10. Which block will have the greatest final velocity?
(A) Block M
(B) Block 2M
(C) They will have the same final velocity.
11. Which block will have the greatest final Momentum?
(A) Block M
(B) Block 2M
(C) They will have the same final Momentum.
12. Which block will have the greatest final Kinetic Energy?
(A) Block M
(B) Block 2M
(C) They will have the same final Kinetic Energy.
The next two questions pertain to the following situation:
Two blocks are free to move on a horizontal frictionless surface. Block A has a mass M=2kg and is initially moving to the right with a speed of v = 2m/s. Block B has a mass of M=6kg and is initially not moving.
13. If the blocks collide and stick together, what is the final velocity of the two blocks?
(A) 0.5 m/s
(B) 0.8 m/s
(C) 1.6 m/s
(D) 2.3 m/s
(E) 2.6 m/s
14. If the blocks collide and stick together, how much energy is lost during the collision?
(A) 1.2 J
(B) 2.6 J
(C) 3.0 J
(D) 4.5 J
(E) 5.6 J
15. An object slides down a frictionless ramp through a vertical distance h. It emerges with a horizontal velocity at the end of the ramp. The object continues falling through an additional vertical distance h before hitting the floor.
What is the speed of the object just before hitting the floor?
(A)
(B)
(C)
The following four problems refer to the picture below.
A roller coaster of mass, m = 500kg, starts from rest at the top of a 30m high hill. Assume the track is frictionless up until point D.
16. What is the speed of the coaster at the top of the second hill? (point B)
(A) 13.9 m/s
(B) 14.7 m/s
(C) 16.3 m/s
(D) 17.1 m/s
(E) 19.8 m/s
17. What is the acceleration of the roller coaster just after it enters the loop? (point C)
Assume the loop is a circle with a radius of 10m.
(A) 52.9 m/s2 Down
(B) 58.8 m/s2 Down
(C) 46.5 m/s2 Up
(D) 52.9 m/s2 Up
(E) 58.8 m/s2 Up
18. What is the magnitude of the Normal force on the roller coaster at the top of the loop? (point D) Assume the loop is a circle with a radius of 10m.
(A) 12900 N
(B) 14700 N
(C) 15200 N
(D) 15900 N
(E) 16100 N
19. Brakes are applied on the car at point E which use friction to stop the car. How much work is done by friction in bringing the car to rest?
(A) 122,500 J
(B) 147,000 J
(C) 202,000 J
(D) 642,000 J
(E) 980,000 J
Two balls each of mass, m = 0.3kg, are dropped from the same height, h = 2m, above the ground. Ball A contacts the floor and stops. Ball B bounces up to a height of 1.5m above the ground.
20. What is the impulse exerted by the floor on Ball B?
(A) 0.4 kg-m/s
(B) 0.6 kg-m/s
(C) 1.9 kg-m/s
(D) 2.3 kg-m/s
(E) 3.5 kg-m/s
21. Golfers can hit a ball with a velocity much greater than the speed at which the head of their club is moving. If a golfer hits a ball of mass mb = 0.046kg with an initial velocity of 80m/s using a club with a mass mc = 0.30 of traveling at 53m/s what is the final velocity of the club head?
(A) 43.9 m/s
(B) 40.7 m/s
(C) 46.3 m/s
(D) 47.1 m/s
(E) 50.8 m/s
5 of 9 pages
(21problems)