We are studying impulse force. Impulse is the force an object experiences when there is a change in momentum. The change in momentum equals the impulse force times the change in time. What time? The time elapsed as the object changes momentum.
An easy way to demonstrate this is to toss an egg back and forth between two students. How do you reduce the impulse force? Look at the equation in the first paragraph. If a student tosses the egg to another student, the change in momentum is equal to the mass of the egg times the speed at which the other student throws the egg. The catcher can either catch the egg with his hands fixed or he can swing his hands and arms back as he is catching the egg.
If you catch the egg and it stops very suddenly, it will probably crack. This is great fun the first time!
If the catcher swings his hands and arms back as he catches the egg the egg usually does not crack. The difference is much more evident if you catch the egg on a cookie sheet instead of your hands. You can also use a bedsheet.
The key concept to understand is that the momentum is a constant in each situation so if you want to reduce the impulse force you must increase the time it takes to bring the egg from its initial speed to a stop.
There are several great examples in real life such as crush zones designed into the front of a car's frame and body, airbags in your car, etc.
The opposite is also true. If you are hitting a baseball, you only have so much strength. If you want the ball to have more momentum so that it goes further, you have to increase the time the bat is in contact with the ball as you are hitting it. In many sports such as baseball, golf and basketball, this is called follow through.
Have fun with the lab.
No comments:
Post a Comment