In the figure the floor
is frictionless and the applied
Force Fa = 4.9 N needed to hold
the block stationary
at x1 = 12 mm.
a)How much work does the spring force do on the block if the block is pulled rightward from x0 = 0 to x2 = 17 mm?
b)Next the block is moved leftward to x3 = -12 mm. How much work does the spring force do on the block during the displacement? Explain the sign of this work.
Sample Problem 7-7
a) k = - F/x = 408 N/m
Ws = - ½ kx22 = - 0.059 J
b) Ws =1/2 kx22 - ½ kx32 = 30 mJ
