gravitational fields - higher

Question 1

What is a definition for GPE involving gravitational forces

Answer 1

energy stored within the system as a result of the gravitational forces acting between its components and their relative positions

Question 2

What is the gravitational potential Vg

Answer 2

work done per unit mass in bringing a mass from infinity to that point

equation:
Vg = -GM/r

Question 3

gravitational field strength

Answer 3

force experienced by a point mass placed at a point due to the gravitational field

Question 4

what is the qualitative effect of a small viscous drag force due to the atmosphere on the height and speed of an orbiting body?

Answer 4

Height (orbital radius):
- Decreases: friction causes the body to lose some of its Kinetic Energy
- No longer maintains original orbital radius and starts to spiral inwards towards the Earth

Speed:
- Initial increase: due to conservation of angular momentum the body will actually experience an increase in its speed
- In a lower orbit, a greater is speed is needed to maintain a stable orbit against stronger gravitational pull
- Eventual decrease: when the body reaches more dense layers of the atmosphere, it will start to experience a decrease in its orbital speed

Question 5

At infinity, gravitational potential is..

Answer 5

zero.

Question 6

derive the speed to maintain orbit

Answer 6

answer:
Fg = Fc

Gmm/rˆ2 = mvˆ2/r

GM/rˆ2 =Vˆ2/r

v = square root of GM/r

Question 7

Changes in energy when a satellite changes orbit

Answer 7

Higher orbit:
- increase in GPE
- decrease in kinetic (lower orbital speed)
- increase in total energy

Question 8

what are the energy conditions for an orbiting satellite to escape the gravitational influence of a planet?

Answer 8

• total mechanical energy must ne greater than or equal to 0
• the satellite’s kinetic energy must be at least equal to the magnitude of its negative GPE
  or its velocity must be greater than or equal to escape velocity.