Chapter 5 Matter In Motion Section 4 – Gravity: A Force of Attraction pp. 134 - 139

IMPORTANT DEFINITIONS Gravity – a force of attraction between objects that is due to their masses. Weight – a measure of the gravitational force exerted on an object Mass – the amount of matter in an object.

MASS AND WEIGHT Mass and Weight ARE NOT the same thing! WEIGHT MASS

MASS VS. WEIGHT Mass: Expressed in grams or kilograms Does not change no matter where you are Measured using a triple beam balance or an electronic balance Amount of matter in an object

MASS VS. WEIGHT Weight Expressed in Newtons Measure of gravitational force on an object 6 times less on the moon than on Earth Changes when gravitational force changes Measured by using a Spring scale

NEWTON’S LAW OF UNIVERSAL GRAVITATION All objects in the universe attract each other through gravitational force. The size of the force depends on: The masses of the objects The distance between the objects

NEWTON’S LAW OF UNIVERSAL GRAVITATION Gravitational force increases as mass increases. Gravitational force decreases as mass decreases.

NEWTON’S LAW OF UNIVERSAL GRAVITATION Gravitational force decreases as distance between two objects increases. Gravitational force increases as distance between two objects decreases.