# Impulse momentum theorem

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1. Apr 17, 2007

### JMarino

I have a question I am looking for an asnwer: Using the impulse momentum theorum, describe how it is possible to drop an egg from a 2 story high building and not have the egg break.

2. Apr 17, 2007

### Staff: Mentor

Sounds like a homework problem to me. Show your thinking so far.

3. Apr 17, 2007

### JMarino

Well I know we would need to slow down the object gradually to keep intact, such as using a stack of feathers or pillows. How does the theorum apply?

4. Apr 17, 2007

### Staff: Mentor

What is the theorem? What is impulse?

5. Apr 17, 2007

### JMarino

impulse is a factor of both force and time. So the egg hitting the pillows (let's say) is the impulse and for a period of time to slow the egg down?

6. Apr 17, 2007

### Staff: Mentor

Impulse is defined as Force X Time; the impulse-momentum theorem tells you that the impulse exerted on an object (by the net force on it) equals its change in momentum.

For the same impulse, if you arrange for the force to be exerted over a greater time (making Time bigger) by using a pillow (for example), what does that imply about the force being exerted on the egg?

7. Apr 17, 2007

### JMarino

you need less force to stop the object

8. Apr 17, 2007

### Staff: Mentor

Right! If you are willing to take a longer time to stop the egg, then you can use less force. Conversely, by using less force--via a softer surface like a pillow--you need more time to stop the egg.

9. Apr 17, 2007

### JMarino

Thank you for the help!

10. Apr 18, 2007

### JMarino

So I have one more problem to solve. Can you help?
A 0.15 kg baseball moving at +26 m/s is slowed to a stop by a catcher who exerts a constant force of 390 N. How long does it take this force to stop the ball? How far does the ball travel before stopping?
- P=mV = 0.15Kg x 26M/s = 3.9Kgm/s. Then what equation?

11. Apr 18, 2007

### hage567

Look at the first part of post #6 again.