1. A ball is thrown straight up in the air.

When the ball reaches its highest point, which of the following is true?

A. It is in equilibrium.

B. It has zero acceleration C. It has maximum momentum.

D. It has maximum kinetic energy.

E. None of the above 53% 24% 18% 6% 0% It is in eq It ui lib ha riu s z er It m.

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2. A sphere of mass m 1 , which is attached to a spring, is displaced downward from its equilibrium position as shown below left and released from rest. A sphere of mass m 2 , which is suspended from a string of length l, is displaced to the right as shown below right and released from rest so that it swings as a simple pendulum with small amplitude. Assume that both spheres undergo simple harmonic motion.

Which of the following is true for both spheres?

(A) The maximum kinetic energy is attained as the sphere passes through its equilibrium position.

(B) The maximum kinetic energy is attained as the sphere reaches its point of release.

(C) The minimum gravitational potential energy is attained as the sphere passes through its equilibrium position.

(D) The maximum gravitational potential energy is attained when the sphere reaches its point of release.

(E) The maximum total energy is attained only as the sphere passes through its equilibrium position.

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3. An empty sled of mass M moves without friction across a frozen pond at speed v

o

. Two objects are dropped vertically into the sled one at a time: first an object of mass m and then an object of mass 2m. Afterward the sled moves with speed v

f .

What would be the final speed of the sled if the objects were dropped into it in reverse order?

64% (A) (B) (E) v f v f / 3 / 2 (C) v f (D) 2 v f 3 v f 7% 7% 7% 14% (A ) v f / 3 (B) vf / 2 (C ) v f (D ) 2 vf (E ) 3 vf

4. A student obtains data on the magnitude of force applied to an object as a function of time and displays the data on the graph below. The increase in the momentum of the object between t = 0 s and t = 4 s is most nearly

(A) 40 N.s

(B) (C) 50 N.s

60 N.s

(D) 80 N.s

(E) 100 N.s

38% 31% 15% 8% 8% (A ) 4 0 N.

s (B) 50 N .s

(C ) 6 0 N.

s (D ) 8 0 N.

s (E ) 1 00 N .s

5. How does an air mattress protect a stunt person landing on the ground after a stunt?

(A) It reduces the kinetic energy loss of the stunt person.

(B) It reduces the momentum change of the stunt person.

20% 20% 20% 20% 20% (C) It increases the momentum change of the stunt person (D) It shortens the stopping time of the stunt person and increases the force applied during the landing.

(E) It lengthens the stopping time of the stunt person and reduces the force applied during the landing (A ) I t r ed uc es th (B) e k It in red et uc ic.

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6. Two objects, A and B, initially at rest, are "exploded" apart by the release of a coiled spring that was compressed between them. As they move apart, the velocity of object A is 5 m/s and the velocity of object B is -2 m/s. The ratio of the mass of object A to the mass object B, m A /m B , is

(A) (B) (C) 1/1 (D) 5/2 (E) 4/25 2/5 25/4 (A ) 4 /2 5 0% (B) 2/ 5 0% 0% (C ) 1 /1 0% (D ) 5 /2 0% (E ) 2 5/ 4

B.

C.

D.

E.

7. An object of mass m is initially at rest and free to move without friction in any direction in the xy-plane. A constant net force of magnitude F directed in the +x direction acts on the object for 1 s. Immediately thereafter a constant net force of the same magnitude F directed in the +y direction acts on the object for 1 s. After this, no forces act on the object. Which of the following graphs best A.

represents the kinetic energy K of the object as a function of time?

20% 20% 20% 20% 20% A.

B.

C.

D.

E.

8. The two blocks of masses M and 2M shown below initially travel at the same speed v but in opposite directions. They collide and stick together. How much mechanical energy is lost to other forms of energy during the collision?

(A) (B) (C) 3/4 Mv 2 (D) 4/3 Mv 2 (E) Zero 1/2 Mv 2 3/2 Mv 2 20% 20% 20% 20% 20% (A ) Z er o (B) 1/ 2 Mv 2 (C ) 3 /4 Mv 2 (D ) 4 /3 Mv 2 (E ) 3 /2 Mv 2

9. A constant force of 900 N pushes a 100 kg mass up the inclined plane shown below at a uniform speed of 4 m/s. The power developed by the 900 N force is most nearly

(A) 400 W (B) (C) 800 W 900 W (D) 1000 W (E) 3600 W 20% 20% 20% 20% 20% (A ) 4 00 W (B) 80 0 W (C ) 9 00 W (D ) 1 00 0 W (E ) 3 60 0 W