Starter Questions Copy the diagram and label the forces 2.What is the resultant of the forces below? 3. An object has a mass of 2kg. What is its weight on the moon where the strength of gravity is 1.6N/kg? 4. What is your speed if you travel 750m in 25s? 3N 18N 7N

Moments

Learning Objective To understand moments Learning Outcomes All Can calculate moments Most Can use the idea of moments to explain balance Some Can do more complex calculations

Force and rotation pivot A force acting on an object can cause it to turn about a pivot. 100 N pivot What happens to the see-saw when a force is applied on the left-hand side? Does the see-saw turn? If so, clockwise or anticlockwise?

Force and rotation – a moment The left-hand side of the see-saw moves downwards when a force is applied to it – this is an anticlockwise turn. 100 N The turning effect of a force is called a moment.

Do sums to show how you decided. Moments Question Copy this diagram…. 50N 4 metres 2 metres 80N Is the seesaw balanced? Do sums to show how you decided.

Copy and complete When a force acts on an object which is fixed at a __________, it makes the object turn. A door is an example. In this case the _________ is acting as the pivot. The size of the turning force can be calculated using the formula Turning effect = Force x Distance from the pivot It could be measured in Ncm or_____. A turning force is sometimes called a _______________ When a big turning force is needed we can increase the distance to the pivot e.g. using a ____________ spanner longer pivot Nm moment hinge

Using moments A spanner is a lever that can be used to unscrew a nut. The spanner exerts a moment or turning force on the nut. pivot distance from force to pivot force force If the moment is big enough, it will unscrew the nut. If not, there are two ways of increasing the moment.

Using moments – increasing the moment 1. Increase the distance from the force to the pivot – apply the force at the end or use a longer spanner. pivot distance from force to pivot force If the same force is applied over a greater distance, a larger moment is produced.

Questions A spanner is used with a force of 15N at 10cm from the end. What is the turning force (moment) acting?? A door is pushed open with a force of 20N. The handle is 75cm from the hinge (pivot). What is the turning force used? 3. A person of weight 500N sits on a seesaw at 1.5m away from the middle. What is the turning force? 4. A child of weight 200N is sitting on a see saw at 2m from the middle. Where would a person weighing 600N have to sit to make it balance? (A diagram might help)