Self-Test: Dynamics in 1D and 2D Test #1

Suggested Time: 60 minutes

1. A block is on a frictionless incline.

Which of the following is a correct free body diagram for the block?

2. A cart on a frictionless surface is attached to a hanging mass of 8.2 kg.

If this system accelerates at 3.5 m/s2 , what is the mass m of the cart?

 A. 6. 0 kg B. 15 kg C. 23 kg D. 31 kg
3. A 5.0 kg concrete block accelerates down a 34° slope at 4.2 m/s2 . Find the coefficient of friction between the block and the slope.

 A. 0.13 B. 0.16 C. 0.43 D. 0.67
4. A 72 kg skydiver drops from a helicopter and is accelerating downwards at 8.6 m/s2. Find the friction force acting on him.
 A. 86 N B. 620 N C. 710 N D. 1 300 N
5. A student exerts a 120 N horizontal force on a 25 kg carton of apples, causing it to accelerate over level ground at 1.8 m/s2 .

Find the coefficient of friction between the carton and the ground.

 A. 0.31 B. 0.38 C. 0.49 D. 0.67
6. Which of the following is not a statement of one of Newton's laws of motion?

A. For every action force, there is an equal and opposite reaction force.

B. If no net force acts on an object, the object will remain at rest, or continue to move at a constant velocity.

C. The acceleration of freely falling objects is proportional to their mass.

D. If a net force does act on an object, the object will accelerate in the direction of the net force.

7. A 2.0 kg block is sliding down a 15° incline. The coefficient of friction is 0.62. At some position the block has a speed of 7.0 m/s.

What distance d will this block move before coming to rest?

 A. 2.5 m B. 4.0 m C. 4.2 m D. 7.4 m
8. The 4.0 kg block shown accelerates across a frictionless horizontal table at 1.5 m/s2 .

Find the mass of object m1.

 A. 0.61 kg B. 0.72 kg C. 6.0 kg D. 26 kg
9. Two forces act on an object as shown in the diagram.

Which of the following best shows the resultant R of these forces?

10. A 75 kg man stands on a scale while accelerating upwards in an elevator. If the scale reads 850 N, what is the magnitude of the acceleration of the elevator?
 A. 1.2 m/s2 B. 1.5 m/s2 C. 9.8 m/s2 D. 11 m/s2
11. A 45 kg toboggan and rider decelerate on level snow at 0.53 m/s2. What is the coefficient of friction between the toboggan and the snow?
 A. 0.012 B. 0.054 C. 0.22 D. 0.53
12. The tension in the string shown is 12 N. Find the acceleration of mass m1.

 A. 3.0 m/s2 B. 6.4 m/s2 C. 6.8 m/s2 D. 13 m/s2
13. Force F gives mass m1 an acceleration of 4.0 m/s2 . The same force F gives mass m2 an acceleration of 2.0 m/s2 . What acceleration would force F give to the two masses m1 and m2 if they were glued together?
 A. 1.0 m/s2 B. 1.3 m/s2 C. 3.0 m/s2 D. 6.0 m/s2
14. Three masses connected by a light string are arranged on frictionless surfaces, as shown in the diagram below.

The strings pass over frictionless pulleys. Determine the direction and magnitude of the acceleration of m1 .

 DIRECTION OF m1 ACCELERATION (m/s2 ) A. up incline 0.20 B. down incline 0.20 C. up incline 0.43 D. down incline 0.43
15. What minimum horizontal force F will just prevent the 5.0 kg block from sliding if the coefficient of friction between the wall and the block is 0.65?

 A. 6.4 N B. 32 N C. 49 N D. 75 N
16. A 3.00 kg object is being accelerated vertically upwards at 2.80 m/s2 , as shown.

What is the tension in the cord?

 A. 8.40N B. 21.0 N C. 29.4 N D. 37.8 N
17. A 6.0 kg block is held at rest on a horizontal, frictionless air table. Two forces are pulling on this block in the directions shown in the diagram below.

What will be the magnitude of the acceleration on the 6.0 kg block at the moment it is released? (7marks)

18. a) Amanda exerts a horizontal force of 180 N on a piece of rope causing two blocks of mass 20 kg and 40 kg to accelerate. Friction on the blocks is negligible. Find the tension force at X in the rope joining the two blocks together. (5 marks)

b) Bob exerts a force of equal magnitude in the opposite direction on an identical pair of blocks.

How does the tension force at X compare to the value in part a)? (Circle one.) (1 mark)

i) The tension force is the same.

ii) The tension force is greater than in a).

iii) The tension force is smaller than in a).

19. Two objects are connected as shown. The 12 kg cart is on a frictionless 42° incline while the 15 kg block is on a horizontal surface having a coefficient of friction µ = 0.23.

Determine the acceleration of the system of masses. (7 marks)

20. The diagram shows a 4.4 kg mass connected by a string to an unknown mass over a frictionless pulley. The system accelerates at 1.8 m/s2 in the direction shown.

a) Calculate the tension in the string. (2 marks)

b) Find mass m2 . (3 marks)