1. Learning Objective and Success Criteria
Progress Step 1:
Identify levers, pivots and forces in a free-body diagram
Progress Step 2:
Use and rearrange the formula for calculating moments
Progress Step 3:
Explain how tower cranes balance using ideas about moments
Progress Step 4:
Apply ideas about turning forces to solve problems involving equilibrium
Increasing challenge

2. Levers
Forces can move objects by turning them around a pivot. A long bar that pivots is a lever. When you push down on one side, you are applying force. The object on the other end (the load) moves up. Using a lever magnifies the force and makes objects easier to move.
Load moves up when force applied
Force
Load
Pivot

3. Jenny is using a lever to lift this large box.
TASK 1:
Jenny is using a lever to lift this large box.
1. Label the diagram of this with the following key words:
Load
Pivot
Force
2. Do you think it would be easier to lift the box with a shorter lever? Explain your answer.
Extension: Is this a free-body diagram?
Why or why not?

4. As Jenny applies force to the lever, she exerts effort at one end
As Jenny applies force to the lever, she exerts effort at one end. The effort (force downwards) causes the load on the other end of the level to move upwards.
Effort
Load
Pivot

5. distance from force to pivot
moment = force (N) x distance from pivot (cm or m)
pivot
distance from force to pivot
force
If you increase the distance and apply the same force then the moment increases!

6. Use the moments equation to answer the question below
LEARNING CHECKPOINT
Use the moments equation to answer the question below
A mechanic pushes on a spanner with a force of 50N. He pushes on the spanner 40cm from the end of the spanner.
Draw a diagram and label the force, distance and pivot.
Calculate the moment of the force using this information.
c) Would the moment be bigger or smaller if he used a longer spanner? ________________________
Explain your answer to part i.
________________________________________________

7. Learning Objective and Success Criteria
Spec point 8: - draw and interpret free-body force diagrams to represent forces on a particle or on an extended but rigid body, using the concept of centre of gravity of an extended body
Progress Step 1:
Identify levers, pivots and forces in a free-body diagram
Progress Step 2:
Use and rearrange the formula for calculating moments
Progress Step 3:
Explain how tower cranes balance using ideas about moments
Progress Step 4:
Apply ideas about turning forces to solve problems involving equilibrium
Increasing challenge
Barriers to progress?
Mathematical ability
Understanding of centre of gravity, equilibrium and free-body diagrams
New terminology

8. Moment equation f x d The moment of a force is given by the equation:
moment = force (N) x distance from pivot (cm or m)
moment f x d
Moments are measured in Newton centimetres (Ncm) or Newton metres (Nm).

9. When an object is balanced it is in equilibrium
The girl on the left exerts
an anti-clockwise moment
The girl on the right exerts a clockwise moment
When an object is balanced it is in equilibrium

10. = 600 N m For the seesaw above: the anticlockwise moment = 300 N × 2 m
the clockwise moment = 400 N × 1.5 m

11. The counterweight produces a turning force
Cranes have a set of moveable concrete blocks called counterweights on one side of the tower.
The counterweight produces a turning force
A turning force is called a moment.
Without changing the number of concrete blocks, it is possible for the crane to lift a variety of different load weights. Explain why using what you have learnt so far today. Try to use the keywords; force, turning, equilibrium, centre of gravity
Load
Moveable concrete blocks

12. Moveable concrete blocks
The moment from the load is balanced by the moment from the concrete blocks to stop the crane toppling over.
Load
Moveable concrete blocks

13. Calculate the clockwise and anticlockwise moments on this crane
LEARNING CHECKPOINT 3 !
Calculate the clockwise and anticlockwise moments on this crane
25m 5m
Load
Moveable concrete blocks
4000N
20,000N