Every wonder why you have to wear a seat belt or wear a helmet? Let's find out (safely) by experimenting with a ball.
You will need to find:
- a car
- a licensed driver
- a ball
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1. Next time you go for a ride bring a tennis ball with you in the car.
2. Sit in the back seat and put the tennis ball in the seat next to you.
3. Now watch the ball carefully as the car moves. See how it moves around the seat? (Try not to let it get on the floor and roll around. It might roll under the pedals and that would be bad.)
4. Pretty easy huh?
As the car moves forward at 20 mph, everything in the car is moving forward at 20 mph. Everything in the car has the same inertia. If the car were to stop suddenly, everything in the car that’s not bolted down, still moves forward at 20 mph until it hits something. An object at rest tends to stay at rest, an object in motion tends to stay in motion. Right? So, if the car stops quickly, the tennis ball continues to move forward until it hits something. If the car turns, the ball continues to go in the direction it was going a second ago, so it rolls around the seat. What would happen if the car stopped suddenly and you weren’t wearing a seat belt? Yup, you’d fly forward at whatever speed the car was going until you crashed into something in the car. See now why seat belts are your best friend?
Download Student Worksheet
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