Gravitational

Question 1

What is Newtons Law of Universal Gravitation?

Answer 1

The force between 2-point masses is directly proportional to the product of their masses and inversely proportional to the square of their separation

Question 2

What are point masses?

Answer 2

Spherically symmetrical objects of uniform density whose gravitational effect is as if all their mass is concentrated at their cenre

Question 3

What is a gravitational field?

Answer 3

A volume of space within which a mass experiences a non-contact force

Question 4

Define field strength and is it a vector or scalar

Answer 4

A vector quantity- force per unit mass on a test mass

Question 5

What is gravitational field strength equivalent to?

Answer 5

The acceleration due to gravity

Question 6

What does the gradient of a gravitational potential vs radius graph equal

Answer 6

Gravitational Field Strength

Question 7

Define Gravitational Potential

Answer 7

Work done per unit mass to move a mass from infinity to that point

Question 8

Why does the gravitational potential formula have a minus sign

Answer 8

• Because it refers to a mass being brought into the field from infinity and there is zero potential at infinity
• Energy input is needed to move to infinity
• Potential energy falls as object moves from infinity

Question 9

What does a synchronous orbit mean

Answer 9

That the satellite has a time period equal to the time period of the planet its orbiting

Question 10

Characteristics of a Geostationary Satellite

Answer 10

• Same time period as earth
• Orbit along the equator
• Used for telephone and television signals as they move in a fixed position relative to the earths surface

Question 11

Characteristics of an LEO

Answer 11

• Low Earth Polar Orbit
• Passes over the North and South Pole
• Closer to the Earth than a geostationary satellite therefore travels faster
• They are cheaper to launch and require less powerful transmitters as they’re closer to the Earth
• Used for mapping land features, military spying and monitoring ocean currents

Question 12

When do force fields arise

Answer 12

Arise from the interaction of mass, of static charge and between moving charges

Question 13

Differences between gravitational and electrostatic forces

Answer 13

Gravitational is always attractive, while electrostatic can be attractive or repulsive

Question 14

Work done moving a mass formula

Answer 14

ΔW=mΔV, where V is the change is potential

Question 15

Define Equipotential surface

Answer 15

LInes that join surfaces of equal gravitational potential- no work is done moving along an equipotential surface

Question 16

What is the area under a gravitational field strength vs Radius graph equal to

Answer 16

The change in gravitational potential

Question 17

What does Kepler’s 3rd law state

Answer 17

Time Period Squared is directly proportional to the radius cubed

Question 18

What is the total energy of a satellite equal to

Answer 18

The sum of its gravitational potential energy and its kinetic energy

Question 19

If a satellite moves closer to the earth, how does this change its energy

Answer 19

KE increases, so satellite speeds up
GPE decreases- loss of GPE twice gain in KE
Total energy decreases