3.1 Uniform Gravitational Fields

Question 1

What is a gravitational field?

Answer 1

a region where a mass feels a force

Question 2

What kind of a force does a mass feel in this region?

Answer 2

A non-contact one

Question 3

Objects of what interact through gravitational field?

Answer 3

of a mass

Question 4

What does the gravitational field of the sun do?

Answer 4

Keep the planets around it in orbit , by its gravitational ‘pull’

Question 5

Do humans experience a gravitational pull by the earth?

Answer 5

Yes, due to the force called weight (as we have mass)

Question 6

Why do object with a greater mass have a more significant effect on gravitational fields?

Answer 6

As the force felt/provided depends on the mass

Question 7

Any object with a mass will experience a force of what if put within a force field of another object (gravitational field).

Answer 7

of gravitational attraction

Question 8

can gravitational force be both attractive and repulsive?

Answer 8

No, only attractive

Question 9

What do we assume about the gravitational field strength near the surface of the earth?

Answer 9

We assume it is constant and hence we assume the gravitational field is uniform?

Question 10

What is the gravitational field strength defined as?

Answer 10

Gravitational force per unit mass acting on a mass at that point in the field

Question 11

What is the equation for gravitational field strength?

Answer 11

g = F / m 
g = gravitational field strength (Nkg^-1 or kgms^-2)
F = gravitational force (N)
m = mass (kg)

Question 12

what is gravitational field strength approx. at earth’s surface?

Answer 12

9.81 Nkg^-1

Question 13

is gravitational field strength a vector or a scalar?

Answer 13

Vector, it always points towards the centre of mass creating the field

Question 14

Is the gravitational field pointing in the same direction as the force it exerts on objects of mass?

Answer 14

Yes

Question 15

What else can gravitational field strength be taken as near earth’s surface?

Answer 15

The acceleration, since F = ma

Question 16

What is this acceleration often called?

Answer 16

Acceleration due to gravity

Question 17

Is the gravitational field of the earth actually uniform?

Answer 17

No, it is radial but along the surface the change in strength is so little that we consider it to be uniform

Question 18

Does the value of gravitational field strength vary around the world?

Answer 18

Yes, as the earth is not an exact sphere

Question 19

In terms of gravitational potential what is the magnitude of it at earth’s surface?

Answer 19

0, it is said to be an equipotential surface

Question 20

When moving along a equipotential what doesn’t happen?

Answer 20

The work isn’t done

Question 21

What is an equipotential

Answer 21

Region of equal potential

Question 22

Moving from one equipotential to other causes what?

Answer 22

A change in gravitational potential energy (gpe)

Question 23

How do we work out the change in gravitational potential in a uniform field?

Answer 23

g x change in distance

it gives units of Jkg^-1

Question 24

Why are the units Jkg^-1

Answer 24

as gravitational potential is defined as potential energy per unit mass

Question 25

So to work out the change in GPE what do we need to do to equipotential value?

Answer 25

Times it by the mass of the object