Lesson 1 - Pressure and Surfaces

force , area , pressure, pascals

Just this bit

force , area , pressure, pascals

• Start
• Equation recall test and Queen song
• Main
• Tanks v heals
• Pain and Lego blocks
• Drawing pins
• Formula
• Bed of nails demo
• Plenary
• Textbook questions from slide
• Exam questions to recap KS3

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force , area , pressure, pascals

Demo - Bed of nails

Safety

• Bed made of real nails - puncture hazzard!
• Very heavy - do not try to lift without help.
• When lying on the bed of nails the whole body must be lowered onto the nails at the same time.
• If you have never done this demo before ask another member of staff to go through the demo with you before the lesson and practice it.
• Use a rolled up lab coat or similar below the head

Aim

• Students should understand that the pressure on an object (the body) is the results of the force acting (weight of body) and the area it is spread over - small area = large pressure.

Top tips

• Demo to students first
• Wear trousers, not a skirt! (Phil this means you!)
• Only choose sensible students to have a go!!

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Method

• Move bed of nails to a clear area of the floor so all students can see.
• Use a rolled up lab coat or similar for a pillow.
• Lower yourself into a “crab” position (see pic) then lower yourself slowly onto the bed of nails.
• The whole body must touch the nails at the same time - DO NOT sit down on it first then lie back!
• Discuss why you can lie on the bed of nails comfortably without injury.
• Get back up the same way - lift whole body at the same time if you can - do not sit up!
• Ask students if any of them would like to try - closely supervise how the student lies down and gets back up.

force , area , pressure, pascals

Lesson 1 - Pressure and Surfaces

Recall check:

Write the formula to calculate:

• E_e
• Power
• Efficiency
• Weight

Write the units of:

• Velocity
• Density

force , area , pressure, pascals

Lesson 1 - Pressure and Surfaces

Check your answers:

• E_e = ½ke²
• Power = energy/time
• Efficiency = (useful energy / total energy in) x 100
• Weight = mass X gravitational field strength

Units for:

• Velocity - m/s
• Density - kg/m³

force , area , pressure, pascals

Lesson 1 - Pressure and Surfaces

Learning objectives:

• To describe the effect on the pressure of changing the area of contact or weight acting on a surface

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• To apply the pressure equation to make calculations

force , area , pressure, pascals

Which has the largest weight?

force , area , pressure, pascals

Which one is the most likely to sink into soft ground? Why?

force , area , pressure, pascals

Why does it hurt so much when you step on one of these?

force , area , pressure, pascals

Drawing pins

Can you push your thumb into the wall?

Why can you push this into the wall with your thumb?

Why does it hurt so much if you use it the wrong way round?

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force , area , pressure, pascals

Pressure

Pressure is caused when objects exert contact forces on each other, or when a fluid exerts a force on an object in contact with the fluid.

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What is a fluid?

A substance with no fixed shape which yields easily to external pressure. A liquid or a gas

force , area , pressure, pascals

Pressure

Pressure is measured in pascals (Pa)

pressure (Pa) = force (N)

area (m²)

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p = F

A

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1 Pa = 1 N/m²

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force , area , pressure, pascals

Hilarious (?) joke:

force , area , pressure, pascals

Bed of nails v drawing pin

How does this work?

force , area , pressure, pascals

Who wants to have a go?

force , area , pressure, pascals

force , area , pressure, pascals

force , area , pressure, pascals

KS3 recap exam questions

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Exam technique: If it tells you in the question to use information from a diagram this means that there is a piece of information in there that you need to find the answer. Remember to show your working.

force , area , pressure, pascals

Check your notes

force , area , pressure, pascals

Logos / symbols

force , area , pressure, pascals