Unit 8 Review: Circular Motion, Gravity, and Friction

Please turn in HW: Friction and count your stamps from the last two units. Below are the review problems for the Unit 8 test, which is on Thursday.

A ladybug sits halfway between the axis and the edge of a turntable. What happens to its linear speed if:

a. The RPM rate is doubled?
b. it sits on the edge of the turntable?
c. Both a and b happen?

What path would you follow if you fell off the edge of a rotating merry-go-round?

The faster the earth spins, the less a person weighs; whereas the faster a space station spins, the more a person weighs. Explain.

If the gravitational forces of the sun on the planets suddenly disappeared, in what kind of paths would they move? Be specific!

If the moon were twice as massive, would the attractive force between the earth and the moon be twice as large? Between the moon and the earth?

If you stood atop a ladder that was so tall that you were twice as far from the earth's center as you are now, how would your weight compare to its present value?

The planet Jupiter is more than 300 times as massive as Earth, so it might seem that an oject on the surface of Jupiter (if it had a surface) would weigh 300 times as much as on Earth. But it so happens that an object would scarcely weigh three times as much on the surface of Jupiter as it would on the surface of the earth. Can you come up with an explanation? (Hint: Let the terms in the equation for gravitational force guide your thinking.)

What is the cause of friction, and in what direction does it act with respect to the motion of a sliding object?

If the force of friction accting on a sliding crate is 100N, how much force must be applied to maintain a constant velocity? What will be the net force acting on the crate? What will be the acceleration?

What is the mass and what is the weight of a 10 kg object on the earth? What is its mass and weight on the moon, where the acceleration of gravity is 1/6 that of the earth?