Potential gradients

Question 1

What are equipotentials?

Answer 1

surface of constant potential

therefore no work need to be done to move along an equipotential surface

Question 2

How do hillwalkers use equipotentials?

Answer 2

controur lines are lines of constant potential

equal heigh above sea level

so a hillwalker following a controur line has constant potential energy

Question 3

How does the gain of gpe change as radius increases?

Answer 3

gravitational field strength becomes weaker

so the gain of gpe per metre of heigh gain becomes less

i.e. away from the Earth’s surface the equipotentials for equal increases of potential are spread further apart

Question 4

Why are the equipotentials horizontal near the surface?

Answer 4

the gravitation field over a small region is uniform

Question 5

What is the potential gradient at a point in a gravitational field?

Answer 5

change of potential per metre at that point

Question 6

what is the equation for a change of potential over a small distance?

Answer 6

the potential gradient = ΔV / Δr

Question 7

how does the gpe change of a mass that has been moved upwards

Answer 7

gpe must increase

• ny am equal and opposite force F acting through the distance Δr
• by an amount of energy equal to the work done by F -
  ΔW = FΔr

Question 8

Why is the equation for gravitation field strength negative of the potential gradeint?

Answer 8

shows that g acts in the opposite direction to the potential gradient