A soft ball is rolling in the inclined pipe (we made a paper pipe with gift wrapping paper) and it hits the car. The car then moves on the Hot Wheels track. What type of friction occurring in this?

Length of tube: 30 inches.

Length of Hot Wheels track: 48 inches.

Weight of ball: 7.4 grams.

Weight of car: 30.2 grams.

Also, when the car is falling from the table track, what type of friction is involved? what are the two surfaces touching each other?

Expert Answers

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There are four types of friction. The four types of friction are rolling friction, static friction, sliding friction, and fluid friction. Static friction prevents surfaces from sliding or slipping across each other. It's the force that keeps a car from sliding down a steep hill that it might be parked on. Another way to think about it is that static friction is the friction that holds things in place. Since the above question asks about a rolling ball and a falling car, static friction doesn't apply.

The rolling ball does have friction, however—has rolling friction. The question seems to indicate that the car is falling off of the table to the ground. In this case, the car is experiencing fluid friction because it is moving through a fluid (air). If this question is asking about the friction involved when the ball hits the car, that is tough to answer without seeing the actual interaction. It it is likely to be sliding friction or static friction. If the ball hit the car and slid over/off of the car, then it is sliding friction. If that seems odd, think of a bowling ball that has just been thrown down the lane. It slides on the smooth wood for a bit before beginning to roll. If the ball struck the car and stopped spinning completely, the frictional force would be static friction. The ball and car "gripped" each other.

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