Please solve all:

Multiple choice

9. When analyzing dynamics problems, free-body diagrams

a. should always be used

b. are more useful when analyzing horizontal forces than when analyzing vertical forces

c. should include only the forces that are directly responsible for the acceleration

d. should be used only when objects are accelerating

e. only apply to objects in equilibrium

10. The free-body diagram of a block being pushed up a rough ramp is best represented by

a. A b. B c. C d. D e. E

11. A 24-kg traffic light is suspended from the midpoint of a cable suspended between two poles. The angle between the cable and the pole is 80 at both poles. The net force acting on the traffic light has a value of

a. zero b. 47 N c. 82 N d. 2.4 10² N e. 4.6 10² N

12. An elevator accelerates downward. What is the relationship between the gravitational forceF_g acting on the elevator and the tensionF_T in the cable that supports the elevator?

a. |F_g| = |F_T| b. |F_g| > |F_T| c. |F_g| < |F_T| d. |F_g| |F_T| e. |F_g| |F_T|

13. An object sits at rest on a ramp. As the angle of inclination of the ramp increases, the object suddenly begins to slide. Which of the following explanations best accounts for the object's movement?

a. The coefficient of static friction has decreased sufficiently.

b. The force of gravity acting on the object has increased sufficiently.

c. The component of gravity along the ramp has increased sufficiently.

d. The friction has decreased sufficiently while the normal force has remained unchanged.

e. The normal force has increased sufficiently.

14. A passenger on a Ferris wheel of diameter 22 m makes one complete revolution every 45 s. What is the passenger's centripetal acceleration?

a. 19 m/s² b. 13 m/s² c. 0.43 m/s² d. 0.21 m/s² e. 0.068 m/s²

15. The diagram below shows a rock on the end of a string being whirled around in a circle in the horizontal plane. The motion is viewed from above and the stone is rotating clockwise. What are the directions associated with its instantaneous velocity and instantaneous acceleration, respectively?

a. south, east b. east, west c. south, south d. west, west e. south, west

Short Answer:

17. Newton's third law talks about forces always acting in pairs with the two forces of any pair being equal in strength and opposite in direction. Does this imply a "balanced" force situation and, if so, how is it possible to ever accelerate anything?[4]

18.Describe how "artificial" gravity can be produced on board an orbiting space station. Discuss the physics of the situation.[4]

19. An object with a mass of 15 kg rests on a frictionless horizontal plane and is acted upon by a horizontal force of 30 N.[4]

(a) What is its acceleration?

(b) How far will it move in 10 s?

(c) What will be its velocity after 10 s?

20. If the coefficient of friction is 0.30, how much horizontal force is needed to pull a mass of 15 kg across a level board at a uniform velocity?[C=3]

21. A 200 g ball on the end of a string is rotated in a horizontal circle of radius 10.0 m. The ball completes 10 rotations in 5.0 s. What is the centripetal force of the string on the ball?[A=5]