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 113. The mean score was 76.4; the median was 77. The exam period was 90 minutes. Click here to see page1 page2 of the formula sheet that came with the exam.

Unless told otherwise, you should assume that the acceleration of gravity near the surface of the earth is 9.8 m/s^{2} downward and ignore any effects due to air resistance.

A block of 10 kg rests on the (horizontal) floor. The coefficient of kinetic friction between the block and the floor is 0.1. You push horizontally on the block with a force F = 30 N.

What is the work done on the block by the force F after the block has moved a distance d = 2 m (in the same direction of the force on the floor).

(a) 20 J (b) 30 J (c) 40 J (d) 50 J (e) 60 J

(a) smaller (b) larger (c) the same

(a) yes (b) no

(a) v = 0 (b) v = mgh (c) v^{2} = 2gh

Two 80 kg skiers, A and B, race on a pair of trails down a mountain. Both trails drop a vertical distance of 100 m. Skier A chooses a trail that zigzags back and forth and has a total length of 1000 m. Skier B chooses a trail that heads straight down the steepest part of the mountain and has a total length of 250 m. Ignoring friction and air resistance, which skier is moving faster at the bottom of the mountain?

(a) A (b) B (c) A and B have the same speed.

(a) A (b) B (c) A and B get to the bottom at the same time.

(a) 175 W (b) 196 W (c) 229 W (d) 344 W (e) not enough information given

A 1.0 kg hammer moving at 3 m/s strikes an initially stationary 10 kg metal block head-on and bounces straight back at a speed of 0.5 m/s. What is the speed of the block after the collision?

(a) 0.11 m/s (b) 0.27 m/s (c) 0.35 m/s (d) 0.54 m/s (e) 0.99 m/s

(a) elastic. (b) inelastic. (c) completely inelastic.

(a) 50 N (b) 100 N (c) 200 N (d) 300 N (e) 800 N

(a) 0 m/s (b) 1 m/s (c) 2 m/s (d) 3 m/s (e) 5 m/s

(a) 0 m/s (b) 25 m/s (c) 50 m/s (d) 100 m/s (e) 150 m/s

(a) mechanical energy was not conserved (b) total energy was not conserved (c) both (a) and (b)

(a) zero. (b) positive. (c) negative.

There are two identical looking disks A and B. A and B have the same mass M_{A} = M_{B}, but the moment of inertia I_{A} of A around its symmetry axis is larger than that I_{B} of B. A and B are released gently from the same height on the incline as illustrated below.

Suppose the slope is frictionless. Which disk reaches the bottom of the incline first? (Note: M_{A} = M_{B} and I_{A} > I_{B})

(a) A (b) B (c) A and B arrive simultaneously.

There is a very light stick of length 3 m. At its one end is an almost point like mass of 5 kg, and at the other end of the stick is another almost point like mass of 9 kg. The stick with two masses is hung from the ceiling with two strings so that it is horizontal as illustrated below. (The dotted line segment in the figure is for the second question below.)

Find the tension T in the right string.

(a) 0 N (b) 49 N (c) 69 N (d) 88 N (e) 127 N

(a) T increases. (b) T does not change. (c) T decreases.

(a) F = Lt / (2R) (b) F = L / (2Rt) (c) F = L / (2t) (d) F = L / (Rt) (e) F = Lt / R

At one end of a massless wire with the partially circular shape shown in the figure is a mass M = 2 kg. The other end is on a fulcrum O, and this balancing toy is stationary. That is, the mass is sitting vertically below the fulcrum O. What is the net torque around the corner A? The angle θ is π/6 and R = 0.5 m.

(a) -RMg (b) -RMg / 2 (c) 0 (d) RMg / 2 (e) RMg

(a) 0 (b) 0.5 kg·m^{2} (c) 1.0 kg·m^{2} (d) 1.5 kg·m^{2} (e) 2.5 kg·m^{2}

(a) increases. (b) decreases. (c) stays the same.

If the floor and the slope are perfectly frictionless, the disk slides without rolling. The largest vertical displacement of the center of mass of the disk is h as shown in the figure.

If instead the floor and the incline have friction, the disk rolls without slipping. What is the largest vertical displacement of the center of mass, if the translational speed of the disk on the floor is the same as before?

(a) 0.5 h (b) 0.67 h (c) 0.75 h (d) h (e) 1.5 h

(a) 33 N (b) 67 N (c) 98 N (d) 131 N (e) 164 N