# How long the ball remains in contact with the ground when dropped

ehild
Homework Helper
How would you do it?

ehild

Interesting .

Do you mean normal from ground is equal to kX_e ?

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ehild
Homework Helper
Interesting .

Do you mean normal from ground is equal to kX_e ?

I do not mean anything. I just would like to know your opinion. I want to learn how to include normal force. :tongue:

ehild

Hmmm... I can see you are enjoying pulling my leg .

But I think normal equal to kx makes sense as kx is the force with which the spring pushes the ground .So you were right in your assessment ehild
Homework Helper
Hmmm... I can see you are enjoying pulling my leg .

Of course :tongue:
But I think normal equal to kx makes sense as kx is the force with which the spring pushes the ground .So you were right in your assessment Add to it that the ball (or spring) is in equilibrium. The force of gravity and the normal force balance each other. mg-N=0.

The interaction between the ground and spring is the normal force from the ground and the spring force by the spring. They are of equal magnitude and of opposite direction. So N=kXe.

ehild