Forces Types of forces Mass and weight Forces and motion Friction Contents Forces Types of forces Mass and weight Forces and motion Friction Summary activities

Gravitational attraction Gravity is an attractive force that exists between all masses. The larger the mass, the greater the gravitational attraction. The greater the distance between masses, the smaller the gravitational attraction. The Earth has a large mass and so produces a strong gravitational force. The Moon is kept in orbit around the Earth by the pull of the Earth’s gravity.

Gravity and weight The pull of the Earth’s gravitational force on an object is called weight. The Moon also has a gravitational force. Why is the weight of an object on the Moon less than the weight of the same object on the Earth? The Moon is smaller than the Earth and so the pull of the Moon’s gravity is weaker than the pull of the Earth’s gravity. This means that the weight of the object is less on the Moon.

Mass and weight 1 kg What is the difference between mass and weight? mass = 1 kg 1 kg weight = 10 N Mass is the amount of matter that makes up an object. The mass of an object is always the same, wherever it is in the Universe. Weight is a force due to the pull of gravity on an object. The weight of an object will vary depending on where it is in the Universe. The units of mass are kilograms (kg). The units of weight are newtons (N).

Mass and weight – true or false?