Why is physics so confusing! I don't even know where to start!?

Question

A 50.0g block is placed on a vertical spring; it compresses the spring by 10.0cm. It is then pushed down a further 20.0cm and released.

a) Determine the spring constant.

b) Relative to its lowest position, what is the max. height reached by the block if it is not connected to the spring.

c) What is the maximum extension of the spring if the block is attached to the spring?

Can someone help me?

Answer 1

F=-kx   where x is the change in length of the spring and k is the spring elastic constant.  The force is equal to the weight of the block.  Therefore:

mg=-kx

-mg/x=k

Use the conservation of energy to solve the last two.  The energy stored in the compressed spring is equal to the amount released.  The distance the block moves can be found using the work-energy equations.  Same for the last, the only thing except you must keep the spring in the final state.

Answer 2

I'm confused too.  Do they explain what they mean by spring constant?  I'm thinking it's a number connected with Earth's gravitational acceleration in this question (since they are giving you the info for mass and compression).

Something that has to be calculated with the 0.05kg and 0.1m, taking into consideration our 9.8m/s.  That'll tell you how elastic that spring is.

That's a start.

Hope that questions like that one don't discourage you from liking the subject.