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Year 7 & 8 TOC

Force

Balancing acts

LO: Investigating the effects of applying different forces to familiar object

When it comes to forces, its all about balance. There are many different forces all around us, but how do they interact. Why aren’t we floating up into the air or being crushed into the ground?

Force can be balanced or unbalanced. Balanced forces are the reason why most objects around us aren’t moving. 

Balanced forces

A balanced force is something that is being pushed and pulled by the same amount. There are many forces around us, but most of them don’t cause movement. This is because they are balanced. Think about a tug of war. 2 teams are pulling against each other. If neither team moves, the forces are balanced. If one team wins, the forces are unbalanced. 

Unbalanced forces

Unbalanced forces are very important. When forces are unbalanced, they allow objects to move. You can see the effect of unbalanced forces on an object if there is a change in the speed, direction or shape of the object.

  • A rocket engine will propel an object forward very quickly, 
  • A parachute, will slow the an object down.
  • When on a motor bike, you lean to one side to turn corners. Turning the bike, creates friction between the tyres and the road, changing the direction of the bike.

A rocket engine will propel an object forward very quickly

When on a motor bike, you lean to one side to turn corners. This creates friction between the tyres and the road, changing the direction of the bike.

A parachute, will slow the an object down.

Consider a weight lifting. The lifter needs to exert more force on the weights than gravity is. To show difference forces we use arrows. Weak forces are show by short arrows, while strong forces are shown as long arrows. 

Combining forces

Some times an object is too heavy and you just can’t lift it on your own. Instead you may get a few friends to help you lift it. All this extra force could be enough to move the object. 

The net force is the combination of all the forces acting on the object. For balanced forces, the net force is 0, like a stationary object.

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