Gravitational Fields

Question 1

Define Gravitational Potential

Answer 1

Work done per unit mass

Question 2

Why is Gravitational Potential negative?

Answer 2

• You have to do work against the grav field to move an object out of it.
• The further you are from the centre of a radial field, the small Vgrav
• At an infinite distance from the mass, the grav potential will be 0

Question 3

Define the Law of Gravitation

Answer 3

F = GMm/r^2

Question 4

Define Gravitational Field Strength

Answer 4

Force per unit mass

Question 5

Differences between G and E field

Answer 5

• Grav fields cannot be shielding, E fields can.

- Grav forces are always attractive, E fields can be repulsive.

Question 6

The bucket is half filled with water and swung. The water stays in the bucket, even at the top of the circular path, as long as the speed of the bucket exceeds a certain
value. Explain why.

Answer 6

A centripetal / unbalanced force is needed because the water is moving in a circular path. At the highest point the unbalanced force is weight of water plus reaction from
bucket. The minimum force needed towards the centre of the circle is the weight of the water.