1) A student decides to move a box of books into her dormitory room by pulling on a rope attached to the box. She pulls with a force of 134 N at an angle of 28.0° above the horizontal. The box has a mass of 20.0 kg, and the coefficient of kinetic friction between the box and floor is 0.300. (a) Find the acceleration of the box. ______ m/s2 (b) The student now starts moving the box up a 10.0° incline, keeping her 134 N force directed at 28.0° above the line of the incline. If the coefficient of friction is unchanged, what is the new acceleration of the box? ________ m/s2, up the incline       2) Neglecting frictional forces on the trailer, determine the following. (Indicate the direction with the sign of your answer. Take the forward direction to be positive.) (a) the net force on the car  _______ N (b) the net force on the trailer  _______ N (c) the force exerted by the trailer on the car  _______ N (d) the resultant force exerted by the car on the road magnitude  _______ N direction  _____° (below the horizontal from the forward direction)

A 100-kg box is towed to move horizontally from rest by a constant force P=200 N. The kinetic friction is μk =0.1. The angle of the force P is θ=30° with respect to the horizontal direction.  The acceleration due to gravity is g=9.81 m/s2.   (5) Calculate the magnitude of the the friction force F= ___(N)  (two decimal places).

2. Three blocks on a frictionless horizontal surfsce are in contact with eachother as shown below. A force F is applied to block 1 as shown. (a) Draw a free body diagram for each block. (b) Determine the acceleration of the system in terms of m1, m2, m3 and F. (c) Determine the net force on each block. (d) Determine the contact force each block exerts on its neighbors. (e) If |F| = 96N and m1 = m2 = m3 = 12kg, give numerical answers to the questions above. Do your answers make sense intuitively? mi mz M3

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