A 40-kg box is being pushed along a horizontal smooth surface. ...

[pragya sharda]

A 40-kg box is being pushed along a horizontal smooth surface. The pushing force is 15 N directed at an angle of 15 below the horizontal. What is the magnitude of the acceleration of the crate?
 
  A) 0.16 m/s2
  B) 0.36 m/s2
  C) 0.47 m/s2
  D) 0.39 m/s2
  E) 0.68 m/s2

Question 2

A solid ball of mass 1.0 kg and radius 10 cm rolls with a forward speed of 10 m/s when it comes to a hill. There is enough friction on the hill to keep the ball from slipping as it rolls up.
 
  (a) How high vertically up the hill can the ball roll before coming to rest?
  (b) How high vertically could the ball go if the hill were totally frictionless?
  (c) How is it that the ball can go higher with friction than without friction?

[jasonq]

Answer to Question 1

B

Answer to Question 2

(a) 7.1 m (b) 5.1 m
(c) With friction, all the initial kinetic energy (translational and rotational) goes into potential energy. Without friction, only the translational kinetic energy goes into potential energy; the ball keeps spinning at the same rate as it goes up, even at the top.

[pragya sharda]

TY

[jasonq]

You're welcome