1. When a vehicle is moving with constant velocity, (assume there is friction) then:

a. all the forces acting on the vehicle are in the direction of motion

b. there are no forces acting on the vehicle

c. the sum of the external forces is zero

d. inertia is the only force acting on the vehicle

e. none of the above

2. A 5 kg crate is accelerated at 1 m/s²by a horizontal force of 20 N. What friction force acts on the object?

a. +5 N

b. -5 N

c. +15 N

d. -15 N

3. A 900 N crate slides at constant velocity across the floor when a 171 N force is applied to the crate. What are the friction forces on the crate?

a. zero

b. 17.4N

c. 171 N

d. 729 N

f. none of the above

4. The measure of an object's resistance to a change of motion is:

a. weight

b. energy

c. mass

d. density

e. none of the above

5. A box with a weight of 981 N is sitting on a scale in an elevator that is accelerating upward at 4 m/s2. What does the scale read?

a. 691 N

b. 1381 N

c. 1972 N

d. 3924 N

e. none of the above

6. When a car is pushed by a tractor with a force F, the car exerts a force against the tractor that:

a. is zero if the car is not moving

b. is 2F if the tractor is moving

c. depend on the relative masses of the tractor and the car

d. is F in all cases

e. none of the above

7. The mass of an object is a measure of:

a. force

b. energy

c. inertia

d. momentum

e. none of the above

8. A net force of 30 N is moving a mass with an acceleration of 15 m/s². What is the mass of the object?

a. 2 kg

b. 7.5 kg

c. 0.2 kg

d. 15 kg

9. A ball is thrown horizontally from the top of a cliff. During its flight the forces acting on the ball are (ignore air resistance):

a. both gravity and the throwing force

b. gravity only

c. the throwing force only

d. cannot be determined

10. The earth attracts a mass with a 500 N force. The mass attracts the earth with a force:

a. of 500 N

b. that is very small

c. that is equal to zero

e. none of the above

11. If the same force is applied to a 7 kg object and a 21 kg object then:

a. the 21 kg object accelerates 3 times faster than the 7 kg object

b. the 7 kg object accelerates 3 times faster than the 21 kg object

c. both objects accelerate at the same rate

d. none of the above is true

12. A crane is lifting 1,000-kg mass upward with an acceleration of 1.0 m/s². What is the tension in the cable?

a. 9,810 N

b. 10,810 N

c. 8,810 N

d. 13810,100 N

e. none of the above