{Year 2} Chapter 3 - Gravitation (Halfway down pg47)

Question 1

Why does the moon have a smaller surface gravity than the Earth?

Answer 1

As it is a less massive body

Question 2

What is Newton’s Law of Gravitation?

Answer 2

F = (m1)(m2)G / r^2

Question 3

What is G?

Answer 3

The universal constant of gravitation - 6.67 x 10^-11

Question 4

When can Newton’s Law not be applied, and why?

Answer 4

When the two masses are irregularly shaped unless a complicated summation of the forces is made - since the law only works for point masses, or spheres since they act as if their mass was concentrated in the middle

Question 5

What law does gravity, like light, obey?

Answer 5

The inverse square law

Question 6

What is a gravitational field?

Answer 6

A region in space in which a massive object experiences a gravitational force

Question 7

What is field strength?

Answer 7

The strength of the gravitational field measured in N/kg. Field lines represent the direction and strength of the field

Question 8

What is the equation for gravitational field strength?

Answer 8

g = F/m

Question 9

What happens to the gravitational field near the surface of a planet?

Answer 9

It becomes very nearly uniform - meaning that the field is of the same strength and direction everywhere

Question 10

What is the difference in the way gravitational field lines are drawn when the field is half as powerful?

Answer 10

The lines are half as prevalent/half as many of them

Question 11

When is capital M used in equations in gravitation?

Answer 11

For the mass of a large object such as a star or a planet

Question 12

What is the equation for the volume of a sphere?

Answer 12

V = 4/3 x Pi x r^3

Question 13

What is the equation for gravitational potential energy?

Answer 13

Grav. pot. = mass x gravity x difference in height

Question 14

What is gravitational potential difference?

Answer 14

The gravitational potential energy difference per kilogram. Gravitational potential and potential difference have units of J/kg. It’s symbol is Delta V

Question 15

What is an equipotential surface?

Answer 15

A surface along which if you move, the gravitational potential stays the same

Question 16

What is the equation which links gravitational fields and potential?

Answer 16

g = - Delta V / Delta h

Question 17

What is escape velocity?

Answer 17

The minimum velocity an object must have at the surface of a planet to escape the pull of gravity using its own kinetic energy

Question 18

What is the set of equated equations or single one that one can use to calculate the escape velocity for a planet?

Answer 18

1/2mv^2 = m DeltaV = GMm/r OR v^2 = 2GM/r

Question 19

What is the equation linking velocity^2 and G?

Answer 19

v^2 = GM/r

Question 20

Which is faster - a larger or smaller orbit?

Answer 20

The smaller orbits are faster

Question 21

What is the equation linking time period and 4Pi^2?

Answer 21

T^2 = (4Pi^2/GM)r^3

Question 22

Why can’t GPE = mgh be used for satellites or large objects?

Answer 22

As the large distance changes in height they would go through would result in a fluctuation in the strength of the gravitational field strength - g would not be constant

Question 23

What is the point in an object’s orbit that is closest to the Sun called?

Answer 23

The perihelion, and the furthest away the aphelion

Question 24

When an object such as a comet moves in an elliptical orbit, what happens to its energy?

Answer 24

It stays the same, although its speed changes