A massless spring with force constant
580 N/m is fastened at its left end to a vertical
wall, as shown below.
The acceleration of gravity is 9.8 m/s
2
.
7 kg 5 kg
580 N/m
Initially, the 7 kg block and 5 kg block rest
on a horizontal surface with the 7 kg block in
contact with the spring (but not compressing
it) and with the 5 kg block in contact with the
7 kg block. The 7 kg block is then moved to
the left, compressing the spring a distance of
0.2 m, and held in place while the 5 kg block
remains at rest as shown below.
7 kg 5 kg
k 0.2 m
Determine the elastic energy U stored in
the compressed spring.
Answer in units of J.