# A-level Physics (Advancing Physics)/Gravitational Potential/Worked Solutions

G = 6.67 x 10^{−11} m^{3}kg^{−1}s^{−2}

g = 9.81 ms^{−2}

**1. What is the gravitational potential at the Earth's surface? (mass of Earth = 5.97 x 10 ^{24} kg,radius of Earth = 6371 km)**

**2. Taking the Earth's surface as V _{grav} = 0, what is the gravitational potential 2m above the ground?**

**3. A 0.2 kg firework reaches a gravitational potential relative to the ground of 500Jkg ^{−1}. If the firework is 30% efficient, how much energy was expended to get there?**

However, this is only 30% of the energy expended, so:

**4. Express gravitational potential in terms of gravitational force.**

**5. Draw the equipotentials and field lines surrounding the Earth.**