Question

# 12. A box is stationary on the floor. Consider the following forces A. a downward force...

12. A box is stationary on the floor. Consider the following forces

A. a downward force from the earth on the box

B. an upward force from the floor on the box

C. An upward force from the box on the earth

D. a downward force from the box on the floor

Which two pairs of forces constitute an action-reaction pair?

a. A and B   b. B and D   c. C and D   d. A and C

13. The stability of an object increases when its

a. center of gravity is closer to its support and its area of support is small

b. center of gravity is closer to its support and its area of support is large

c. center of gravity is farther from its support and its area of support is large

d. center of gravity is farther from its support and its area of support is large

14. The force friction acting on an object

a. is directed along its direction of motion

b. is directed against its direction of motion

c. is directed along the normal force

d. can have different directions

15. The coefficient friction between the tires on a car and the road is 0.3 If a car of mass 800 kg is accelerating along a straight, horizontal road at 2 m/s2.

The force of friction on the car is

a. 240 (N)    b. 1600 (N)    c. 2400 (N)    d. 4000 (N)

16. The net force on the car is

a. 0 (N)    b. 1600 (N)    c. 2400 (N)    d. 4000 (N)

17. The force pushing the car forward is

a. 1600 (N)    b. 2400 (N)    c. 4000 (N)    d. 5600 (N)

18. A hockey puck of mass 150 grams is at rest on the ice rink when it is hit with a force of 20 N. If the force of friction that acts on the puck from the ice is 0.075 N, what is the coefficient of friction between the puck and ice?

1. 0 because it is on Ice    b. .005    c. .05   d. .5

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