In the figure the floor is frictionless and the applied
= 4.9 N needed to hold the block stationary
= 12 mm.
How much work does the spring force do on the
block if the block is pulled rightward from x
0 to x
= 17 mm?
Next the block is moved leftward to x
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
= - ½ kx
= - 0.059 J
- ½ kx
= 30 mJ