Simply put, inertia is an object's ability to resist a change in motion. For example, a ball rolling on a table will continue to roll on that table FOREVER until some other force acts on it. Now, that force could be the ball rolling off the edge of the table and the force of gravity taking over. If you're rolling a ball down a long, flat road, the ball will slow down due to friction. If you could make the road friction-less, that ball would continue to roll until the end of time, assuming no other forces act on the ball.
Consider riding in a car. Your body moves with the car. Your body has inertia in the forward direction. When you slam on the brakes, your body has that inertia which causes your body to continue to move forward. If you're wearing a seat belt, the seat belt is the outside force that stops you. If you're not wearing a seat belt, inertia continues to carry your body forward until you smash into the windshield.
Consider the following picture which I found posted on George Takei's facebook page:
Assume the truck was moving at 50 mph. That means your body is moving at 50 mph. It has inertia. So does the big stone in the trailer, which is also moving at 50 mph. If the truck slams on the brakes, both your body and stone have inertia and want to continue moving forward at 50 mph. The seat belt prevents the person from moving forward, but the stone itself has no "seat belt" other than the front of the trailer. Since the stone continues moving forward, it had enough force to break through the front of the trailer.
Moral of this story? Understand inertia. No one wants a big stone slamming into the back of their head!
i think the stone had momentum which caused the damage. don't understand inertia though so could be the same thing. guess it depends on whether you are the driver or a stationary onlooker?
ReplyDeleteHi Hugh. Both the stone and truck have inertia, as does your body in the truck. When you slam on the truck brakes the truck stops. Your body continues to move forward and is stopped by the seat belt, if you're wearing it. If not, your body flies forward into the windshield. If the big stone block is not secured with its own "seat belt", it will fly through the truck when the brakes are hit, due to the block's large inertia.
ReplyDelete