Gravitational Fields

Question 1

What does Newton’s law of gravitation state ?

Answer 1

Any object with a mass will attract another mass with a force inversely proportional to the square of the distance between them and directly proportional to the product of the two masses

Question 2

What would happens to the force when the distance between the masses doubles ?

Answer 2

The force would decrease by a factor of 4

Question 3

What is the equation produced of the attractive force as a result of the masses ?

Answer 3

F=GMm/ r^2

Question 4

What is the gravitational constant ?

Answer 4

6.67*10^-11

Question 5

What is the units of the gravitational constant ?

Answer 5

Nm^2kg^-2

Question 6

How do you work out the gravitational field strength ?

Answer 6

GM/r^2 = g or f/m

Question 7

When you substitute g into the equation for the force of attraction produced by the masses what does it tell us about g ?

Answer 7

G is the acceleration (F=ma=mg)

Question 8

How can you define gravitational field strength?

Answer 8

The gravitational force exerted per unit mass on a point within the field.

Question 9

What direction would the gravitational field strength lines be drawn ?

Answer 9

In the same direction as the gravitational force (towards the centre of the mass

Question 10

What do gravitational field lines represent?

Answer 10

The direction of force experienced by a mass placed in a field.

Question 11

What is a radial field ?

Answer 11

A field that exists between point masses and around uniform spheres

Question 12

Why does the field lines considered to be uniform on earth ?

Answer 12

Towards the surface they appear to be parallel to each other

Question 13

What are uniform field ?

Answer 13

A field where the value of the field strength is the same at all points . The field lines will be equally spaced and parallel to each other.

Question 14

What is gravitational potential energy ?

Answer 14

Gpe is what is stored when work is done against the gravitational field to move an object in the opposite direction

Question 15

What is the gravitational potential energy in a uniform field ?

Answer 15

Ep = mgh - for small distances

Question 16

What is the gravitational potential energy in a non- uniform field ?

Answer 16

We take the Ep at r = ♾️ as 0 so have negative values for Ep.

Ep= - GMm/ r (sub GM/r^2 as g in mgh )

Question 17

What stays consistent with both uniform and non-uniform fields ?

Answer 17

The Ep increases along with the height.

Question 18

What is gravitational potential ?

Answer 18

The gravitational potential energy given to a unit mass in moving a point from infinity to a point within the field

Question 19

How can you work out the gravitational potential?

Answer 19

-GM/r as it remains the same for any object at a distance r

Or Ep/m

Question 20

What the gravitational potential of a point within a gravitational field equal to ?

Answer 20

The work done per kilogram of mass in bringing the mass from infinity to the point

Question 21

What is the gravitational potential at infinity ?

Answer 21

0

Question 22

What quantity is gravitational potential?

Answer 22

Scalar

Question 23

What is constant when a mass moves along the equipotential line ?

Answer 23

The gravitational potential energy as well as the gravitational potential as no work is done when something moves at right angles to the field

Question 24

What angles are equipotential surfaces to the gravitational field?

Answer 24

Right angles

Question 25

What happens to v when r increases when plotting v against r ?

Answer 25

V decreases to produces a ln graph starting from the radius of the object

Question 26

What does the gradient of a v against r graph give ?

Answer 26

-g ( gravitational field strength)

As change in v / change in r means u divide v by r giving you the field strength.

Question 27

How can you work out g at a certain distance by using a v against r graph ?

Answer 27

By drawing a tangent at that distance and calculating its gradient *-1

Question 28

What does the area under a g against r graph give ?

Answer 28

The gravitational potential as g*r gives us v