True-false questions are worth 2 points each, three-choice multiple choice questions are worth 3 points each, five-choice multiple choice questions are worth 6 points each. The maximum possible score is 98. The exam period was 90 minutes. The mean score was 71.9; the median was 74. Click here to see page1 page2 of the formula sheet that came with the exam.

A 2-kg disk and a 4-kg disk slide on a horizontal frictionless surface. The 2-kg disk is initially traveling in the positive x-direction at 7 m/s, the 4-kg disk is initially traveling in the positive y-direction at 5 m/s. The disks collide and stick together as shown in the figure below.

What is the final speed | v | of the two disks after the collision?

(a) | v | = 4.1 m/s (b) | v | = 8.6 m/s (c) | v | = 12 m/s

(a) θ = 37° (b) θ = 55° (c) θ = 64°

(T) True (F) False

A massless 100-cm stick has a 2-kg ball on one end, and an 8-kg ball on the other as shown below.

Where is the center of mass located for this system?

(a) 50 cm to the right of the 2-kg ball (b) 70 cm to the right of the 2-kg ball (c) 80 cm to the right of the 2-kg ball

(a) I = 2.5 kg m^{2} (b) I = 5.0 kg m^{2} (c) I = 10 kg m^{2}

A uniform one-meter bar has a mass of 10 kg. One end of the bar is hinged to a building, and the other end is suspended by a cable that makes an angle of 45° above the horizontal as shown in the picture.

What is the tension T in the cable?

(a) |T| = 69 N (b) |T| = 98 N (c) |T| = 113 N (d) |T| = 129 N (e) |T| = 132 N

(a) | F_{y} | = 0 (b) | F_{y} | = 26 N (c) | F_{y} | = 49 N (d) | F_{y} | = 72 N (e) | F_{y} | = 98 N

A three-meter plank has a mass of 15 kg and is supported by two saw-horses as shown below. The first saw-horse is at the right end, and the second saw-horse is two meters to the left of the first.

What is the force that the left saw-horse provides to support the plank?

(a) F_{2} = 73.5 N (b) F_{2} = 110 N (c) F_{2} = 147 N

(a) F_{1} = 37 N (b) F_{1} = 73.5 N (c) F_{1} = 147 N

(a) d = 2.35 m (b) d = 2.5 m (c) d = 2.75 m

(a) F_{2} = 73.5 N (b) F_{2} = 123 N (c) F_{2} = 245 N

A 4-kg block, starting at rest, is moved a distance d = 3 meters across a horizontal frictionless floor by a force F at an angle θ = 31° with respect to the floor, as shown in the figure. The force does work in the amount of 44 J on the block during the displacement.

What is the magnitude of the force?

(a) 7 N (b) 15 N (c) 17 N

(a) v = 1.5 m/s (b) v = 2.3 m/s (c) v = 3.8 m/s (d) v = 4.7 m/s (e) v = 5.1 m/s

A skier starts at rest from the top of a hill at height h above ground. The skier glides down the hill to point A and continues up a second hill 9 meters high and back down the other side. Her entire trip up to point C is frictionless. After point C, there is friction between her skis and the ground. She comes to a complete stop 53 meters after point C, at point D.

Of the three listed below which is the smallest value of the height h so that the skier reaches point C?

(a) 5 m (b) 10 m (c) 15 m

(a) v = 4 m/s (b) v = 13 m/s (c) v = 21 m/s (d) v = 35 m/s (e) v = 44 m/s

(a) 0.1 (b) 0.2 (c) 0.3 (d) 0.4 (e) 0.5

A 2-kg block is released from rest and slides down an incline with angle θ = 41°. The coefficient of kinetic friction between the block and the incline is 0.27. The block goes down a distance D along the incline where it hits a wall and rebounds. Just before it hits the wall, the block has a speed v = 3 m/s.

What is the distance D traveled by the block on the incline on its way down?

(a) 1 m (b) 2 m (c) 3 m (d) 4 m (e) 5 m

(a) 3 J (b) 5 J (c) 9 J (d) 11 J (e) 13 J

(a) 100 N (b) 200 N (c) 300 N

Two 5-kg blocks are connected by a taught, massless string that runs over a massless pulley. The first block is on a horizontal frictionless surface and the right block slides down a frictionless incline. The blocks start from rest with the right block at the top of a frictionless incline that has a height of 0.8 m, as shown.

Calculate the speed of the right-side 5-kg block after the it reaches the bottom of the incline, assuming that the left-side 5-kg block does not hit the pulley.

(a) v = 2.8 m/s (b) v = 4.0 m/s (c) v = 4.6 m/s

(a) v = 1.1 m/s (b) v = 2.1 m/s (c) v = 2.3 m/s (d) v = 2.7 m/s (e) v = 3.2 m/s

(a) larger than that in the previous problem. (b) equal to that in the previous problem. (c) smaller than that in the previous problem.

A bullet with an initial velocity of 280 m/s in the +x-direction penetrates an initially stationary block of mass 11 kg and emerges on the other side with a final velocity of 70 m/s in the +x-direction. The velocity of the block after the collision is 0.2 m/s, also in the +x-direction. Assume the block slides on a horizontal frictionless surface.

What is the mass of the bullet?

(a) 0.01 kg (b) 0.02 kg (c) 0.03 kg (d) 0.04 kg (e) 0.05 kg

(a) smaller than 0.2 m/s. (b) equal to 0.2 m/s. (c) larger than 0.2 m/s.