How Much Force to Apply on m1 to Make m2 Jump Off the Table?

[thoff430]

Homework Statement

Hey there,

We assume that the spring got no mass and there are no frictions. If you want to push down just as hard on m1 that if you release ... m2 will be just about to jump and leave the table?

Homework Equations

Newton and Hooke are our very best friends :)

The Attempt at a Solution

1. F > (m1 + m2) * g

or

2. F > m2 * g ?

Im a bit confused, as m1 is already pushing on the string even if there is no extra force... but how much do I have to push down for myself on m1? My guess is that 1 would be to total amount of force "pulling" on m2, but the force needed to get this right, would be 2, as m1 is supporting.

Thanks in advance

 

[ehild]

What is the condition that m2 jumps and leaves the table? What can you say about the net force acting on it at that instant?

ehild