Question

You drop a block from rest from a height h=3 m. The block lands on the spring at height h1 = 1.5 meters (spring constant = 160Nm) and compresses it 0.5 m before the block and spring momentarilty come to rest. (The spring then pushes the block upward.) What is the mass of the block?

If needed, g=10ms2.

I tried using kinematics (constant acceleration) for the first part of the motion (before the block hits the spring) and got v = 5.42218. Then I used conservation of energy for the block-spring system and got m = k*x^2/v^2 = 1.36054 but obviously it was wrong.

Answer 1

I just did one problem from you, the xo and vo sping

Answer 2

In total the block fell from 3 to 1 meters off floor
so change in gravitational potential
m g h = m g (2)

there it is stopped so that energy is now stored in the spring which compressed half a meter

m g (2) = (1/2) k x^2 = 80 (1/4) = 20
so
20 m = 20
m = 1 kg

Answer 3

riiight I forgot the gravitational potential energy. Thanks!

Answer 4

1.0 Kg