Which force pulls objects towards the center of the Earth?

What keeps the planets in orbit around the Sun?

If you drop a stone and a feather at the same time in the absence of air, what happens?

The weight of an object is the force of:

Which of the following will decrease if you go to the Moon?

Friction always acts in which direction?

Which of the following surfaces will have the least friction?

Which of the following is used to reduce friction?

On which planet would you weigh the least?

Which type of friction is present when you push a heavy box but it does not move?