Question

A 0.150-kg frame, when suspended from a coil spring, stretches the spring 0.070m . A 0.200-kg lump of putty is dropped from rest onto the frame from a height of 30.0cm

A)Find the maximum distance the frame moves downward from its initial position.
So far i got .17 and .24 but it says thats wrong. I am confused please help!

Answer 1

The 0.15kg frame has a weight of 1.47N and this causes an extension of 0.07m.
This gives a spring constant of 21N/m
A 0.2kg lump of putty dropped from 0.30m will have KE (= PE) of 0.589J
When the putty lands on the platform the spring will extend and this energy is stored in the spring.
The energy stored in a spring is 0.5F x ext or,
since k(spring constant) = F/e
F = k x ext then energy stored = 0.5 x k x e^2
The spring will stop extending when the 0.589J of KE have been stored (absorbed)
so 0.589 = 0.5 x 21 x e^2
This gives e (extension) of 0.237m
This is the maximum extension and the spring will oscillate.