# Vertical spring physics

• fiziksfun
In summary, the conversation discusses the forces acting on two blocks connected by a spring and pushed down to oscillate. The question is how to find the maximum acceleration the blocks can obtain while remaining in contact. The force of the spring, gravity, and normal force are all considered, and it is determined that the net force is equal to the normal force minus the force of gravity. When the block loses contact, the normal force becomes zero. Using Newton's second law, an equation can be written to find the magnitude of the normal force.

#### fiziksfun

An 5 kg block is fastened to the top of a vertical spring (perpendicular to the floor) with a spring constant of 1000 N/m. A 3 kg block sits on top of the 5 kg block.

The springs are pushed down so that they oscillate.

I need help finding the magnitude of the maximum acceleration the blocks can obtain while still remaining in contact. I have no idea where to begin.

HINT: Consider the forces acting on the 3kg block, which force will be zero when the blocks lose contact?

Ok so when the blocks lose contact, the force of the spring-mass will be equal to the force of gravity on the 3 kg block.

M(3)*a=-2mg, is this correct?

You've still not answered my first question. What are the forces acting on the top block?

Last edited:
The forces acting on the block are gravity and the force of the spring, correct? Or friction??

fiziksfun said:
The forces acting on the block are gravity and the force of the spring, correct?
Correct, but what I was trying to get at is that the force of the spring acts through the normal force exerted on the block. Hence, the net force acting on the block is $N - mg$. Can you now use this information to write an equation using Newton's second law?

ma = N - mg

but what is the magnitude of the normal force ??!? kx !?

fiziksfun said:
ma = N - mg
Correct! And what do you know about the normal force when the block leaves the surface of the 5kg block?