1. The gravitational potential at the Earth's surface is about -60 MJ kg-1 . The work done in lifting a 2kg mass into deep space away from the Earth is therefore:

• A. +60MJ
• B. -60 MJ
• C. +120MJ
• D. -120MJ

2. A planet that is twice as massive as the Earth but only has 1/2 the radius will therefore have a gravitational potential at the surface of about ...

• A. -15 MJ kg-1
• B. -60 MJ kg-1
• C. -120 MJ kg-1
• D. -240 MJ kg-1

3. Which of these statements about the magnitude of the gravitational field strength at any point is true?

• A. gravitational field strength = gravitational potential gradient
• B. gravitational field strength = gravitational force gradient
• C. gravitational field strength gradient = gravitational potential
• D. gravitational field strength gradient = gravitational force

4. Which of these diagrams best shows the shape of equipotential surfaces around two identical binary stars? 5. Two objects of mass m and 2m are located at distances r and 2r from a planet as shown. The ratio gravitational potential at m is: gravitational potential at 2m
• A. 2
• B. ½
• C. 4
• D. ¼

6. A satellite lands on a small spherical asteroid. To escape the pull of gravity of the asteroid on the return journey, the satellite needs to be launched with a certain escape velocity. Data for the launch is available, including:

• I. The mass of the asteroid.
• II. The mass of the satellite.
• III. The radius of the asteroid. image: nasa.gov
Which of these 3 factors affects the escape velocity of the satellite?
• A. I and II
• B. I and III
• C. II and III
• D. All three statements

7. To stay in a circular orbit of radius r around the Earth, a satellite of mass m has a potential energy of Ep. If the satellite now moves into a higher orbit of radius 2r, the potential energy..

 A. increases by GMm r
 B. decreases by GMm r
 C. increases by GMm 2r
 D. decreases by GMm 2r

8. When in orbit, how is the gravitational potential energy (Ep) of a satellite related to the kinetic energy (Ek)?

• A. Ep= Ek
• B. Ep= 2Ek
• C. Ep = - Ek
• D. Ep = - 2Ek

9. As the satellite moves into a higher orbit, how does the total energy and the kinetic energy change?

 total energy kinetic energy A increases decreases B increases increases C decreases constant D decreases decreases