ForcesForces

A force is a Or a

PushPull

What forces do you know?

Magnets

The world is full of pushes and pulls. Pushes and pulls are forces in action. A magnet is special; it can push or pull something without touching it.

Magnets have centres of push and pull called the poles of the magnet.

Poles that are the same repel (push) each other. Poles that are different attract (pull) each other.

Magnets also attract some metals.

http://www.bbc.co.uk/schools/revisewise/science/physical/12_act.shtml

Springs

Springs exert forces, too. They push back if you squeeze them; and pull back if you stretch them. When you let them go, they go back to their original shape.

Gravity

Gravity is a force which acts on every object – The larger the object the greater the gravity. The sun is the largest thing in the universe. It keep our planet in its orbit.

The Earth is a huge object too. Its gravity pulls things towards it.

Friction

Friction is a force that slows movement. It can slow your movement down the park slide (solid against solid), or swimming through the water (solid against liquid) or dropping with a parachute (solid against gas). Friction takes place between the tiny bumps and pits in solid materials. So even materials that look and feel very smooth can be slowed by friction.

Rub your hands across the table. What stops them moving?

What happens when you rubYour hands together.

Where is friction important?

Friction Experiment

A car was rolled down a ramp. The children measured how far it travelled. They then tested different materials like carpet and paper.

Which material has the most friction?

How could they make it a fair test?

Material Distance Travelled (cm)

Wood 75Plastic 68Carpet 15Lino 59Metal 89Crepe Paper 35

Wood 75Plastic 68Carpet 15Lino 59Metal 89Crepe Paper 35

Results

Air ResistanceIf you were to drop two objects at the same time like a hammer and a feather and a ball which would you expect to hit the floor first?

Why does this happen?

Air resistance is very useful for slowing things down through the air

http://www.channel4.com/weblogic/essentials/science/physical/quiz.jsp?unit=Forces+in+action&unitShortName=forcesaction&rand=1069676415290

http://www.bbc.co.uk/schools/revisewise/science/physical/12b_act.shtml

Now youv’e learnt about Air resistance, friction and gravity try this

http://www.bbc.co.uk/schools/revisewise/science/physical/13_act.shtml

Force direction/balaned/unbalanced forces

Label the forces in the following activity

Measuring Forces

http://www.learnpremium.co.uk/Whiteboardactiv/Science/Keystage2/Year4/Friction/Whiteboard/default.asp

Forces are measured in Newtons after the scientest Sir Isaac

Newton