Paper 2: Gravitational Fields

Question 1

What is a force field?

Answer 1

It is a region in which a body experiences a non-contact force.

Question 2

When are force fields present?

Answer 2

When there are interactions between masses or charges.

Question 3

What type of force is gravity?

Answer 3

It is attracive between all matter with mass.

Question 4

Define Gravitational Field strength

Answer 4

Force per unit mass in a gravitational field. NKg-⁻¹

Question 5

What are some similarities between electromagnetic and gravitational forces?

Answer 5

• both obeys inverse square laws of intensity
• both have euqapotentials
• can be reprwesented via field lines

Question 6

What are some differences between gravitational and electromagnetic forces?

Answer 6

Gravitational forces are only attractive whereas electromagnetic forces can repel or attract according to their charges.

Question 7

What can field lines tell you about a field?

Answer 7

• The direction of the field
• desnity of lines can show the strength

Question 8

What is g in a radial field?

Answer 8

g is the proportionality constant at that point between the force and mass. where g = GM/r²

Question 9

define gravitational potential

Answer 9

potential energy per kilogram
JKg⁻¹

Question 10

What is Gravitational Potential?

Answer 10

potential energy per kg at any point in the field.

Question 11

What is the work done by moving a mass in a field?

Answer 11

Mass × Δ V

Question 12

What is the gravitational potential difference?

Answer 12

Gravitational Pd is trhe energy needed to move a unit mass between equipotentials.

Question 13

Define Gravitational Potential Difference

Answer 13

ΔW =mΔV

Question 14

What is an euipotential? surface?

Answer 14

A surface in which every point on the surface has the same potential.

Question 15

Why is gravitational potential negative?

Answer 15

Work needs to be done to move the object outside of the field.
Since outside the potential is defined as 0, inside the field must be a negative.

Question 16

How is the orbital period related to a radius of a circular orbit?

Answer 16

T² ∝ r³

Question 17

compare the PE and KE of a lower orbit to higher orbit

Answer 17

lower orbit means smaller mass, means lower PE but higher KE.
Higher orbit means larger mass, more potential energy but less kinetic energy.

Question 18

What is the period of a geosynchronous orbit?

Answer 18

Time period of 1 day = 24 hrs = 86400s

Question 19

What is the period of a geosynchronous orbit?

Answer 19

Time period of 1 day = 24 hrs = 86400s

Question 20

What is an escape velocity?

Answer 20

v = √ 2GM/r it is the minimum speed needed for an unpowered object to leave an orbit and not fall back into the gravitational field due to gravitatinal forces.

Question 21

What is one application of geosynchronous orbits?

Answer 21

They are at the equator. useful for TV and telephone signals as you dont need to adjust the rciever or transmitter as the satellite already does that.