1. FORCES Outcome 4.6 Stage 4

2. overview 1) What is a force? Examples of forces Measuring forces 2) Contact forces 3) Non-contact forces 4) Balanced Forces 5) Unbalanced Forces This symbol means that there is a question on your worksheet to be filled in! It will appear in this corner so you don’t miss anything!

3. what is a force? Nothing moves by itself. Objects must be pushed or pulled! …or a… A force is a…

4. We use forces every day! ActionPush and/or Pull? Pressing a button Climbing a tree Jumping Walking Towing a car Jumping PUSH PULL PUSH PULL PUSH PUSH & PULL PULL PUSH

5. What changes happen when forces are applied? Changing the speed of an object Changing the shape of an object Stopping a moving object Changing the direction of an object Moving a stationary object

6. Forces are measured in Newtons, written as N for short How do we measure a force? http://www.cowetaschools.org/eses/IT/Clipart%20for%20Forces %20and%20Motion%20WebQuest/force%20meter.gif Forces are measured using a Force Meter, which uses a spring The bigger the force, the more the spring stretches Or, we can calculate it using this equation: Force = mass x acceleration

7. Forces can happen between objects………... …or from a distance non-contact (non-contact forces): 1)Electrostatic force 2) Magnetic force 3) Gravitational force …by touching contact (contact forces): Frictional force

8. Forces normally occur in pairs……… These pairs are called Action and Reaction The Action force causes a change Example: car tyres push backwards on the road to move the car forwards The Reaction force is the force that ‘reacts’ to the action force. Example: the road pushes forward against the cars tyres

9. Forces normally occur in pairs……… Action and Reaction forces act in OPPOSITE directions They can be BALANCED or they can be UNBALANCED