Question

3.

a) Find the acceleration of gravity at the height of 2.0 x 10⁶ above the earth.

b) A spherical asteroid that is the size of Texas would have a mass about 2.4 x 10²¹kg and radius of 4.7x 10⁵ meters. Find the acceleration of gravity on this asteroid.
c) Name three controls on a car that control acceleration.

d) Explain how the spin cycle of a washing machine removes most of the water from the wet clothes.

Answer 1

a)

The acceleration due to gravity at this height is given by

b)

The acceleration due to gravity on this asteroid is given by

c) Accelerator, Break, Steering wheel (as acceleration is a vector, even changing direction is changing acceleration.)

d)

It’s not a real force, but it acts like one. Just like in a centrifuge. Or just like you feel in a car going around a sharp curve.

As the clothes move faster and faster, they and the water in them gain momentum. Like anything with inertia, the clothes want to follow Newton’s 1st law, which says that objects in motion tend to stay in motion—in a straight line, if possible.

But it’s not possible for the clothes, because the drum they’re in keeps steering them around in a circle. The water, which is more free to move than the clothes are, can move in a straight line, a tangent to the circle. The faster the drum turns, the more force it would take to prevent the water from taking off, and off it goes—made even easier by the fact that there are little holes in the drum through which it can escape.

Of course it doesn’t get very far. After flying off on a tangent, the water collides with the outer drum, drips down to the bottom of the machine, and is pumped out by the water pump.