In 2 experiments, a student pulled each of 3 blocks in a straight line across a flat, horizontal surface.

In Experiment 1, the student measured the pulling force (the force required to move each block at a constant speed) and plotted the pulling force, in newtons (N), versus block mass, in kilograms (kg). The results are shown in Figure 1.

In Experiment 1, the student measured the pulling force (the force required to move each block at a constant speed) and plotted the pulling force, in newtons (N), versus block mass, in kilograms (kg). The results are shown in Figure 1.

In Experiment 2, the student measured the speed versus time of a 2.00 kg block, a 2.50 kg block, and a 3.00 kg block as each block was pulled across the surface with a constant 30 N force. The results are shown in Figure 2.

1. If a block was pulled toward the east, the frictional force exerted on the block by the surface was directed toward the:

A. north.

B. south.

C. east.

D. west.

A. north.

B. south.

C. east.

D. west.

**2.**Based on Figure 2, what is the order of the 3 blocks, from the block that required the shortest time to reach 15 m/sec to the block that required the longest time to reach 15 m/sec ?

**E.**2.00 kg block, 2.50 kg block, 3.00 kg block

**F.**2.00 kg block, 3.00 kg block, 2.50 kg block

**G.**3.00 kg block, 2.00 kg block, 2.50 kg block

H. 3.00 kg block, 2.50 kg block, 2.00 kg block

**3.**Based on Figure 2, what was the approximate value of the acceleration of the 3.00 kg block?

**A.**0.0 m/sec2

**B.**5.0 m/sec2

**C.**15.0 m/sec2

**D.**20.0 m/sec2

**4.**Based on Figure 1, the results of Experiment 1 are best modeled by which of the following equations?

**E.**Block speed (m/sec) = 0.2 × time (sec)

**F.**Block speed (m/sec) = 5.0 × time (sec)

**G.**Pulling force (N) = 0.2 × block mass (kg)

**H.**Pulling force (N) = 5.0 × block mass (kg)

**Answers:**

**1.**D

**2.**F

**3.**B

**4.**J