Thursday 21 st June 2012 Physics: Transport Homework 1

Measuring Forces A force is something that can change the SPEED, DIRECTION or SHAPE of an object. Forces are measured in NEWTONS (N). The size of a force can be measured with a Newton Balance.

The Force of Gravity Everyone knows that when we let things go they always fall down – never up!! Sir Isaac Newton was the scientist who wondered why things always fall down. He decided there must be a force doing this ‘pulling’ – he called this force GRAVITY.

All objects produce a force of gravity. However only massive objects like planets and the Sun produce strong enough forces for them to be noticed. The bigger the object the bigger the force of gravity!! Sir Isaac Newton showed that the force of gravity from the Sun keeps the Earth in orbit (it is like an invisible string between the Sun and the Earth) and similarly Earth’s gravity ‘holds’ the moon.

The force of gravity on any object is actually the weight of the object! So this means that because weight is a force it is measured in NEWTONS! The thing we usually call ‘weight’ and is measured in kilograms and grams is really called the MASS!

Mass and Weight The mass of an object tells us how much ‘stuff’ is in it. It is also to do with the number of particles that make up the object. Mass is measured in kilograms ( and sometimes grams, tons etc.) Weight is measured in Newtons.

Mass and Weight Experiment AIM: To find out if there is a connection between mass and weight. METHOD: Use a Newton Balance to measure the force of Gravity (weight) on different masses.

RESULTS: Mass (kg)Weight (N) My massMy weight

CONCLUSION: The weight of things on Earth is _______ times the mass in kg. Every kilogram on Earth has a weight of _____N. 10

70kg Zelda g = 2N/kg Earth g = 10N/kg “Show Me” RECAP