5.7 gravitational field

Question 1

define gravitational field strength

Answer 1

the gravitational force per unit mass exerted on a small test mass placed at the point

Question 2

define gravitational potential energy

Answer 2

of a mass at a point is defined as the work done by an external force in bringing a small test mass from infinity to that point

Question 3

define gravitational potential

Answer 3

the work done per unit mass by an external force in bringing a small test mass from infinity to that point

Question 4

why is gravitational potential (energy) always negative?

Answer 4

gravitational forces are attractive, and gravitational potential at infinity is zero, which is the maximum. work is done against gravity in bringing the mass to the point.

Question 5

relationships between f, g, u and potential

Answer 5

• f = mg
• u = m potential
• g = d potential / dr
• f = du/dr

Question 6

relationship between GPE and KE of a mass at a point

Answer 6

KE = 1/2 (-GPE)

Question 7

define geostationary orbits

Answer 7

orbits made by satellites about earth’s axis such that these satellites would appear stationary when observed from a fixed location on earth