Question

3. Pre-Lab Conceptual Question: You are trying to get a good night of sleep before a physks eram, unfortunately your roommates decide to throw a loud party in the house. You are lying in bed but your bedroom doors open and you are tired enough that you don't wish to get up to close the door. The only way to close the door is to throw either a bouncy ball which bounces off the door or a clay ball which does not bounce of the door - you are tired enough that you can ONLY throw one, not both of you are successful in closing the door you get a good night of sleep and you do extremely well on the exam. Assuming both balls have the same mass, which ball bouncy or clay) would you throw to close the door? Give reasons for your choice and remember that your physics exam score depends on it! Record your choice in step 17 of the lab.

Answer 1

Solution : let the mass of each ball be m and they strike to the door with V velocity then the momentum imapeted by the ball to the door

In case of clay ball = final - initial

Momentum = 0 - MV = -MV ( the ball stick to the door )

Change of momentum of door = MV .............(1)

Now for second bouncing ball

Momentum = -MV -MV = -2MV ( the ball bounces back with same velocity )

Change of momentum of door = 2MV

You can see that in the second case the momentum imparted is more than first so we should throw the ball which would bounce back because it would exert more force on the door.