A-level Physics (Advancing Physics)/Gravitational Forces/Worked Solutions

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1. Jupiter orbits the Sun at a radius of around 7.8 x 1011m. The mass of Jupiter is 1.9 x 1027kg, and the mass of the Sun is 2.0 x 1030kg. What is the gravitational force acting on Jupiter? What is the gravitational force acting on the Sun?

2. The force exerted by the Sun on an object at a certain distance is 106N. The object travels half the distance to the Sun. What is the force exerted by the Sun on the object now?

So, the new force is 4 MN.

3. How much gravitational force do two 1 kg weights 5 cm apart exert on each other?

In other words, ordinary objects exert negligible gravitational force.

4. The radius of the Earth is 6360 km, and its mass is 5.97 x 1024kg. What is the difference between the gravitational force on 1 kg at the top of your body, and on 1 kg at your head, and 1 kg at your feet? (Assume that you are 2m tall.)

This is why it is acceptable to approximate the acceleration due to gravity as constant over small distances.