Gravitational Fields

Question 1

Definition for gravitational potential.

Answer 1

The work done/energy REQUIRED to move a unit mass from an infinite distance to that point in the field.

Question 2

Is gravitational potential a scalar or vector quantity?

Answer 2

SCALAR and always negative. Tends to 0 as r tends to infinity.

Question 3

Why is gravitational potential negative?

Answer 3

• Because the field is doing the work.
• When we do work we see that as positive energy doing work AGAINST the field therefore work done by the field is negative.

Question 4

How do you prove a field is not uniform.

Answer 4

The change in gravitational potential is NOT directly proportional to the change in distance. Therefore line is curved.

Question 5

What is the gradient of a gravitational potential vs distance graph?

Answer 5

Gravitational field strength g

Because g= - Δ𝑉/Δr

Question 6

What is escape velocity equal to and why?

Answer 6

v² = 2GM/r
Because:  Δ𝑊 = 𝑚ΔV    V=-GM/r    Ek=1/2mv²
Ek = mV.  
m cancels then x2. 
ΔV = V at planet surface because V∞ = 0.