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