6.2 Newton’s Law of Gravitation

A planet has triple the mass of Earth and a third of its radius. What is the gravitational field strength on the surface of the planet?

The diagram below shows three uniform masses in a straight line.

The resultant gravitational force on the 1 kg mass is zero if the distance x is:

The gravitational force between two identical uniform spheres of mass M is F when the distance between them d.

If the radius of each sphere is x, what is the correct expression for mass, M?

A satellite of mass m is placed in a geostationary orbit. If the Earth’s angular velocity is ω rad s^–1, what is the circumference of the satellite’s orbit?

A spherical planet of uniform density has two times the mass of the Earth and three times the average radius. The magnitude of the gravitational field strength at the surface of the Earth is g. What is the gravitational field strength at the surface of the planet?

The inverse square law means that halving the radius of a planet results in quadrupling the gravitational field strength at its surface.

The centres of two planets are separated by a distance R. The gravitational force between the two planets is F. What will the force between the planets be when their separation increases to 4R?

A mass at point P gives rise to a gravitational field strength g at point X as shown.

An identical mass is placed at point Q as shown.

What is the resultant gravitational field strength at X in this new situation?

A spacecraft travels away from Earth in a straight line with its motors shut down. At one instant, the speed of the spacecraft is 5.7 km s^-1. After a time of 1000 s, the speed is 5.2 km s^-1. The gravitational field strength acting on the spacecraft during this time interval is:

Which of the following statements about uniform gravitational fields is incorrect?