SP221/2141&4341
Chapter 4 Homework
Due Monday September 26, 2016
Question 1: (Tipler & Mosca Problem 4-80) Figure 4-58 shows a 20-kg block sliding on a 10-kg
block. All surfaces are frictionless and the pulley is massless and frictionless. Find the acceleration
of each block and the tension in the string that connects the blocks. [10 points]
Question 2:A block of mass m1 =6.0 kg sits on a frictionless ramp that is inclined at θ=31◦ . An
ideal rope connected to the block runs down the ramp, over an ideal pulley to a hanging block of
mass m2 =3.5 kg. (a) What is the magnitude of the acceleration of the blocks? What is the tension
in the string? [10 points]
6.0
31◦
3.5 kg
kg
SP221/2141&4341
Chapter 4 Homework
Due Monday September 26, 2016
Question 3: A frictionless wedge is inclined at an angle θ with respect to the horizontal. The wedge
is accelerating to the right with a constant acceleration of magnitude a. A block of mass m rests
on the wedge and is also pulled up the incline by a spring. (a) Draw a free-body diagram for the
block. (b) Assume that the block remains stationary with respect to the wedge (i.e. the block is
also accelerating to the right with magnitude a). Solve for Fs , the spring force acting on the block
in terms of g, m, a, and θ. Fs should be positive if the spring is pulling the block up the wedge and
negative if it is pushing the block down the wedge. (c) What is Fs when θ = 0◦ ? What is Fs when
θ = 90◦ ? (d) Solve for a in terms of m, g,and θ such that Fs =0. (i.e. At what acceleration would the
block remain stationary with respect to the wedge even if there were no spring there?) [20 points]
m
~a
θ