14. Block B rides on top of Block P, as shown in the figure below. A person attaches a spring to Block P and pulls block P to the right. Assume that static friction between the two blocks keeps Block B from slipping off and there is a small amount of kinetic friction between block P and the ground. Just after block B is released, which of the following statements must be true? M's a. The static friction force acting on block B points to the left. b. The force exerted by the spring on block P points to the left. The free body diagram associated with block P should include the weight of block B. d. The static friction force acting on block P points to the left. When the spring is released, the system should behave as an underdamped harmonic C. e. oscillator.

18. A child sits on a sled at the top of a hill, the hill makes an angle of 20° with the horizontal. The child's mass is 40kg. Use us = .1 and 4.03 a. b. Draw a free body diagram for this system. Does the child accelerate down the hill? *i.e., check that the coefficient of static friction is vercome by the component of the childs weight in the direction the child would accelerate. If they do, what is their acceleration? *use coefficient of kinetic friction in sum of the forces balance if the child moves.

while tom pushes a 40 kg box in horizontal direction along the classroom floor with a 100 N force, the box is moving in a straight line with constant speed of 0.5 m/s. Ignor air resistance when answering the questions below. a. Write down as much information as you can about the main horizontal forces exerted on the box ( names, directions and if enough information is given, numerical values). b. Write down as much information as you can about the main vertical forces exerted on the box (names, directions, and whenever possible, if enough information is given, numberical values). c. How far did the refrigerator move during those 3 seconds? Explain d. What was the refrigerator's acceleration during that time? Explain