GRAVITYWALT: To understand that gravity is an important pullforce

Gravity:• Is a force that pulls all objects to the centre of the

Earth.

•Holds all things to the Earth’s surface and stops them from floating away.

•When you jump in the air, your energy pushes you off the ground but gravity pulls you back to the centre of the Earth again.

•Keeps Earth within the solar system and the solar system together.

Mass or Weight?• The mass of an object tells us how much material (matter)

it contains. It can be measured in g or kg/pounds or stones. Mass does not change.

• The weight of an object is the force caused by gravity pulling it. It is measured in Newtons (N). Weight can change depending on the gravitational pull of the planet.

•A bigger planet has a bigger gravitational pull.

•An object with a bigger mass, has more gravity acting on it and therefore weighs more.

How much Gravity? On Earth, gravity pulls on every 1 kg with a force of 10N.

On the moon, gravity is one-sixth as strong.

In a spacecraft, there is no gravity so there is no pull on an object and nothing will register on a Newton meter.

Showing Gravity:

On a diagram we can show gravity (or weight) by an arrow towards the centre of the earth.

Showing Gravity:Which arrow is pointing the wrong way?

So who worked it out?It was Sir Isaac Newton that ‘worked-out’ gravity.

He was the greatest mathematician and scientist of his generation.

His Laws of Motion make him one of the greatest English scientists the world has known.

The story goes that he was sitting under an apple tree and an apple fell onto his head. He went to explore why it fell down and came up with a theory and mathematical equation which he named GRAVITY.

Gravity is a force and we measure all forces in Newtons.

The effect of gravity gives us our weight -so our weight should always be measured in Newtons.

Weight is measured using a Forcemeter.

The bigger the weight attached to the Forcemeter, the more the spring inside the Forcemeter stretches.

Newton Meter (also

called Forcemeter,

Spring balance, and

Pull Meter)

Measuring Gravity: