# Homework Help: Physic problem springs

1. Mar 1, 2005

### InFiNiTeX

Physic problem.... springs

A 700g block is released from rest at height Ho(initial) above a vertical spring with spring constant k=400 N/m and negligible mass. The block sticks to the spring and momentarily stops after compressing the spring 19.0 cm.

How much work is done
A) by the block on the spring?
B) by the spring on the block?
C) what is the value of Ho?
D) If the block were released from height 2H0 above the spring, what would be the maximum compression of the spring?

If someone could help me figure where to start and the formulas substituted it would be much appreciated!!!

2. Mar 1, 2005

### stunner5000pt

the work done on the spring is the change i nteh spring's potential energy.
that is given by $$E_{s} = \frac{1}{2} kx^2$$
what is the initial x value and what is the final x value.

the spring did what to the block?? the box fell and it gained _____ and then the spring did something to stop the block. Use energy conservation

$$\Delta K + \Delta U + \Delta E_{s} = 0$$
where K is the kinetic energy and U is the potential energy

you can find the inital velocity Of the block as it hit the spring from that above equation. The work done by the spring is the change in K and U for the block.

now youk now the velocity of the block as it hit the spring.
Now for part 2 again delta K + delta U = 0 this time for the bloc konly give the final velocity, and the initial velocity (read the question), the initial potential energy (unknown) and the final potential energy (since potential is ONLY REFERENCE you can take the final as zero) and you can find Ho

For D just see how Ho affects the spring and work it out. I suggest you use variables for this and not the numbers themselves though it wouldnt make much of a difference