Topic 10.2 – Fields at work – AHL Formative Assessment
NAME: _________________________________ TEAM:__
THIS IS A PRACTICE ASSESSMENT. Show formulas, substitutions, answers (in spaces provided) and units!
The following questions are about gravitational potential energy, potential, and potential gradient.
1. Define gravitational potential.
The gravitational potential is the change in gravitational potential energy per unit mass in moving that
mass from infinity to a point P.
2. Find the change in gravitational potential in moving from Earth’s surface to 3 Earth radii (from Earth’s
center). 2. +4.17107 J
V
g= -GM/r
V
g = -GM( 1 / 3R - 1 / R )
= -(GM/R)( 1/3 – 1 )
= - (6.6710-115.981024/6.37106)( -2/3)
= +4.17107 J
3. The gravitational potential in the vicinity of a planet changes from -0.85×107 J kg-1 to -0.79×107 J kg-1
in moving from r = 1.80×107 m to r = 1.82×107 m. What is the gravitational field strength in that
region? 3. -3.0 m/s2
g = - Vg / r
= - ( -0.79 – -0.85 )107 / ( 1.82 – 1.80 )107
= -3.0 m/s2
Four point masses, each of which has a mass of 875 kg, are arranged in a circle of
radius 2250 m as shown.
4. What is the gravitational potential at the