#### What is being taught lesson by lesson:

- Levers. Look into the way that levers work and what we use them for.
- Calculating the turning effect of levers. Use of term “moment”.
- Machines doing work. Looking into the relationship between forces applied and how far things are moved. Look at pulley systems.
- Pressure. Investigate lots of scenarios and how pressure related to force and area.
- Calculating pressure. Apply the new formula to the situations already met to work out the different pressures involved.
- Atmospheric pressure. Link the atmospheric pressure to the amount of gas sitting above you all pushing down. Look also at the pressures that gases exert inside sealed containers.
- Pressure in liquids. Relate this to the pressure in the atmosphere. Explain in terms of particles why there is more pressure the deeper you dive in the ocean.
- Hydraulic machines. Use what you have learned so far to explain how a car jack works and how a JCB’s scoop moves.

#### Key Terms for this topic (Tier 3 vocabulary)

Lever – pivot – fulcrum – turning effect – moment (turning force) – work done – pulley – pressure – atmospheric – hydraulic.

KS3 Pressure, Moments & Levers

WAre you ready for your assessment in this topic? Try out this simple quiz.

#### What everyone needs to know:

#### Learning:

- Identify an obvious lever and label the effort pivot and load.
- State whether a lever is being used as a force multiplier or a distance multiplier.
- State that a moment is the turning effect caused by a force. State the Principle of Moments.
- Calculate simple moments using the correct units.
- Describe what happens to moments and forces when an object is in equilibrium.
- Investigate the forces and distances involved in pulley systems.
- State that energy is conserved in mechanical systems.
- Describe pressure in terms of a force acting on an area.
- State that pressure is increased when the area is small or the force is large.
- Calculate the pressure acting on a surface with some assistance.
- State that atmospheric pressure acts on all surfaces within the atmosphere.
- State that atmospheric pressure decreases with height above sea level.
- Describe the cause of pressure in liquids in simple terms (e.g. the weight of the water above).
- State that the pressure in liquids increases with depth.
- State that forces can be transferred through liquids because liquids are not easy to compress.

#### Mastering:

- Calculate the speed of objects using the equation and a range of units.
- Describe the rotation of a lever clearly. Describe the function of a wide range of levers including force and distance multipliers.
- State that forces are mechanisms that transfer energy (do work). Describe forces as the mechanism for energy transfer in mechanical systems.
- Investigate the factors that affect the turning effect of a force. Convert length units to calculate the moment of a force. Determine whether an object is in equilibrium by calculating moments.
- Describe the factors that will increase the pressure acting on a surface, and calculate the pressure acting on a surface with some assistance. Describe the cause of pressure in gases in simple terms.
- Use secondary data to investigate the variation of atmospheric pressure with height.
- Describe how pressure within a liquid can produce an upthrust due to differences in pressure.
- Describe the operation of hydraulic machines in terms of movement of the hydraulic fluid.

#### Expanding:

- State that a lever can be used to increase the size of force acting on the load at the cost of reducing the distance the load is moved. Use scale diagrams to describe the forces acting on a lever.
- Calculate the work done by a lever; design an experiment to measure the work done by a lever.
- Rearrange the moment equation to calculate distances and forces. Calculate the total moment when more than one force acts in the same direction of rotation. Determine the missing forces or distances in equilibrium situations.
- Explore systems with more than two forces acting. Calculate work done in mechanical systems. Evaluate systems and identify reasons for energy loss.
- Describe a wide range of applications of high pressure relating them to the area of contact between objects. Describe the relationship between the forces acting on the two cylinders and the cross-sectional area of the hydraulic cylinders. Rearrange the pressure equation to calculate forces and area.
- Provide simple explanations about why pressure decreases with height above sea level.
- Use the particle model to describe the cause of pressure in gases and why pressure increases with depth in a liquid. Compare pressure changes in different fluids.