4.9

·         

4.9 recall and use the relationship between work, force and distance moved in the direction of the force:

       work done = force × distance moved         

Wd = F × d

	<<Work formula.ppt>>
			<<4B1 work done pushing a wheelbarrow.swf>>		<<4B1 work done skiing downhill.swf>>

Work formula.ppt Download this file

4B1 work done skiing downhill.swf Download this file

4B1 work done pushing a wheelbarrow.swf Download this file

Starter - answers

Tell the person next to you...

·         Imagine pushing a king sized bed from one side of the classroom to the other

·         Would it make you feel tired? 

o    Yup!

·         Would you have to work hard to push it?

o    Yup!

·         What could you change so you have to do less work pushing?

o    Anything that decreases the force needed (reduce friction by putting wheels on it, ice under it, etc)

o    Anything that decreases the distance travelled (only push it half way!, etc)

o    So the formula for work must contain force and distance

Plenary Questions

PFY p.54

1

a) Thermal energy travels through the bottom of a pan by convection. The energy is passed from one vibrating atom to the next. All metals are good conducts. Plastic, water and air are poor conductors (good insulators)

b) Convection currents can form when liquids and gases are heated. The cold fluid falls and the hot fluids rises.

c) Energy can travel through empty space by radiation rays, which can be reflected by mirror like light rays. Dull black surfaces are good radiators and good absorbers. Shiny, bright surfaces are good radiators and bad absorbers.

d) A vacuum flask uses silvering to cut down heat transfer by conduction and uses a vacuum to cut down heat transfer by convection and radiation.

4.8

·         

4.8 describe how insulation is used to reduce energy transfers from buildings and the human body

Task 1

·         Use this interactive animations to investigate how different insulation affects the rate of cooling of hot water

<<Cooling of hot water with insulation - interactive.swf>>

Task 2

·         Use these interactive animations to find out about the energy transfers in a house

	<<Types of energy transfers in a house - interactive.swf>>		<<Insulation in a house - % heat losses and savings.swf>>

Task 3

·         Test your knowledge with this quiz

<<Quiz - Types of energy transfers in a house.swf>>

Types of energy transfers in a house - interactive.swf Download this file

Quiz - Types of energy transfers in a house.swf Download this file

Insulation in a house - % heat losses and savings.swf Download this file

Cooling of hot water with insulation - interactive.swf Download this file

4.7

·         

4.7 describe the role of convection in everyday phenomena

Lee cycles towards the sea ... and back worksheet.pdf Download this file

Convection in a room with a radiator.swf Download this file

Objective 4.6: Notes on Conduction, Convection and Radiation from Collins

See the full gallery on Posterous

Answers to Entrance Activity for 4.7

Answers...

1.             What is the most common heat transfer mechanism in solids?

Conduction

2.             What is the most common heat transfer mechanism in liquids and gases?

Convection

3.             What is the only heat transfer mechanism in a vacuum?

(Infra-red) Radiation

4.             Why can't conduction happen in a vacuum?

There are no particles in a vacuum to transfer the vibrations

5.             What happens to the space between the particles in a gas when you heat it?

The space between the particles increases

6.             What happens to the density of a gas when you heat it?

It decreases because the space between the particles increases

7.             Why can't convection happen in a solid?

In a solid the particles are fixed in position and are not free to move