# Physics Space Notes

## Physics Space Notes

Earth’s Gravitational Field
Gravity is a force of attraction that exists between any two masses.
Gravitational field: a ‘region of influence’ in which a mass would experience a force due to the presence of another mass.
For example, the Earth has a gravitational field that draws us to the ground, and is the reason why objects fall if unrestrained.

Acceleration due to gravity on any planet:

Latex formula

Where:

Latex formula is the universal gravitation constant
Latex formula is the mass of the planet
Latex formula is the radius of the planet
Physics Module 1: Space Earths gravitational field.

Example 1

The mass of the Earth is Latex formula (this is found in your data sheet). The radius of the Earth is approximately Latex formula. What is the surface gravity of the Earth?

Solution

Latex formula
Latex formula
Latex formula

Example 2

Jupiter has a mass of Latex formula and a radius of Latex formula. How much would a 65kg man weigh on the surface of Jupiter?

Solution

So the weight of a 65kg man is:

Latex formula
Latex formula
Latex formula
So the weight of a 65kg man is:

Latex formula
Latex formula
Latex formula

Weight

Weight is defined as the force on a mass due to a gravitational field. Mathematically: Latex formula

For example, a 50kg person on Earth has a weight of Latex formula

Gravitational Potential Energy

Gravitational potential energy is the potential energy possessed by a mass due to its position within a gravitational field. By definition, gravitational potential energy is the work (energy) needed to move an object to an infinite distance within a gravitational field. As a result of this definition, all measures of gravitational potential energy are negative values.

When a force is applied to an object and the object moves, we say work has been done on the object
Work is the product of the force and the displacement in the direction of the force,
As we lift an object from the...