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G481.2 Work and Energy Scheme of Work

Module 3:1.3 Work and Energy (Lessons 26-35)






Ref: G481.26

Title: Conservation of Energy

Group

Date

Period

Room

Objectives – by the end of the session pupils should be able to:
(a) define work done by a force;
(b) define the joule;
(c) calculate the work done by a force using W = Fx and W = Fx cos θ;

Keywords:
Work
Energy
Force
Vector

Follows from:
Links to:

Starter – list energy types. State the conservation of energy. Resolving vectors revision.
UFO – what force does it need to go up at a constant speed? What energy has it gained? What is g? (Gravitational field strength) What two factors will determine how much energy the battery loses (and hence the energy transferred to the object)? What is the equation? This suggests that energy transferred = force ´ distance moved in direction of force. This is known as the work done by the force. Now push along the desk (W=Fx – heat as friction)

Development Activity
Derive W=Fx cosθ
Efficiency of a ramp student experiment

Plenary Activity
Go through work questions

Individuals

Resources:
As experiment sheet

Homework:
Lesson 26 HW sheet

2

Evaluation:


 






Ref: G481.27

Title: Energy changes

Group

Date

Period

Room

Objectives – by the end of the session pupils should know:
(d) state the principle of conservation of energy;
(e) describe examples of energy in different forms, its conversion and conservation, and apply the principle of energy conservation to simple examples;
(f) apply the idea that work done is equal to the transfer of energy to solve problems.
(a) select and apply the equation for kinetic energy Ek = ½ mv2;
(b) apply the definition of work done to derive the equation for the change in gravitational potential energy;

Keywords:
 Kinetic energy
Potential energy

Follows from:
Links to:

Starter Activity
Notes
You have established that work = force × distance. Before embarking on the practical work it may help to make the link between initial kinetic energy and work done in deceleration, as clear as possible. A body has 1 MJ of kinetic energy and is decelerated to rest. What is its final K.E? (0 J) Hence, how much work has been done on the body? (1 MJ)
If they have done it: This might be a good point to rehearse the SUVAT equation: v2 = u2 + 2as. Thus when a car is accelerated from u to v m s-1, the change in KE = ½ mv2 – ½ mu2. This just equals the work done by the accelerating force = Fs using Newton’s Second Law:  F = ma. Thus ½ mv2 – ½ mu2   = mas. i.e. v2 = u2 + 2as

Development Activity
Pendulum – idea of conservation of energy
Indy dvd – http://uk.youtube.com/watch?v=rK7xkNGKVP0 through the tunnel; discuss rollercoasters
Questions

Plenary Activity
A slide questions

 

Individuals

Resources:
Big Pendulum Bowling Bowl or similar dangerous object – flaming or with spikes on it or something!!
Indy DVD

Homework:
Lesson 27 HW sheet

3
Don’t get hit by bowling bowl.

Evaluation:


 






Ref: G481.28

Title: GPE to KE

Group

Date

Period

Room

Objectives – by the end of the session pupils should be able to:
(c) select and apply the equation for the change in gravitational potential energy near the Earth’s surface Ep= mgh;
(d) analyse problems where there is an exchange between gravitational potential energy and kinetic energy;
(e) apply the principle of conservation of energy to determine the speed of an object falling in the Earth’s gravitational field.

Keywords:
Energy conservation
GPE
KE

Follows from:
Links to:

Starter Activity
Demonstrate practical. Measuring the speed of a mass falling from different heights.

lesson 28 - gpe to ke\Water_Slide_WMV_V9_001.wmv

Development Activity
Students carry out practical.
Predict and test using pe=ke and rearranging for v.
High jump questions

Plenary Activity

Go through questions

Individuals

Resources:
Light gates, computers, clamp stands, metre rules

Homework:

4

Evaluation:


 






Ref: G481.29

Title: Power

Group

Date

Period

Room

Objectives – by the end of the session pupils should be able to:
(a)define power as the rate of work done;
(b) define the watt;
(c) calculate power when solving problems;

Keywords:
Power
Energy transferred (work done)
Watt (kW)

Follows from:
Links to:

Starter Activity
Define power. A sample calculation; power = force × velocity. A car engine provides a forward force of 1000 N. If the car is travelling at 20 m s-1, what power is developed? In 1 s, the car travels 20 m. Hence we can calculate: Work done in 1 s = force × distance = 1000 N × 20 m = 20 000 J = 20 kJ. Power = work done / time taken = 20 kJ / 1 s = 20 kW.
From this example, you can point out that we could equally have used an alternative form of the equation for power: Power = force × velocity. e.g.   Power = work done / time taken = (force × distance (in direction of the force))/ time taken.
Distance (in the direction of the force) / time taken = velocity so power = force × velocity.
(However, this only works if the velocity is steady, i.e. the ‘force’ is NOT the resultant force on the moving object.)

Development Activity
Student activity – find the power of themselves. Up steps. Lifting weights and press ups.

Plenary Activity
Questions

Individuals

Resources:
Bathroom scales, Flight of stairs, Stop watch, Measuring tape or ruler, Heavy mass (5 kg)

Homework:
Lesson 29 HW sheet

5don’t drop masses on heads! Or trip up steps! Warm up properly.

Evaluation:

 






Ref: G481.30

Title: Efficiency

Group

Date

Period

Room

Objectives – by the end of the session pupils should be able to:
(d)state that the efficiency of a device is always less than 100% because of heat losses;
(e) select and apply the relationship for efficiency Eff. = useful output energy/total input energy ×100%
(f) interpret and construct Sankey diagrams.

Keywords:
Energy
Power
Percentage
Sankey

Follows from:
Links to:

Starter Activity
Efficiency of catching ping pong balls
How can I work out the percentage? Come up with equation: Eff. = useful output energy/total input energy ×100%

Development Activity
Describe the efficiency of a lightbulb and draw Sankey diagram.
Show Sankey diagram of a car
Efficiency if a motor. Get students to find efficiency of a motor and draw Sankey Diagram to show energy losses. (eff = (mgh/Ivt)x100%)

Plenary Activity
Check Sankey Diagrams – draw on board.

Individuals

Resources: Pulley wheels / 100 g masses, string, metre rules, motor, ammeter, voltmeter.

Homework:

6

Evaluation:

 

 







Ref: G481.31

Title: spring constant

Group

Date

Period

Room

Objectives – by the end of the session pupils should be able know:
(a) force in one dimension and can be tensile or compressive;
(b) describe the behaviour of springs and wires in terms of force, extension, elastic limit, Hooke’s law and the force constant (ie force
per unit extension or compression);
(c) select and apply the equation F = kx, where k is the force constant of the spring or the wire;

Keywords:
Hooke’s Law
Stiff, Strain, extension, tension, compression

Follows from:
Links to:

Starter Activity
Demo practical set up

Development Activity
Hooke’s Law practical, Students can carry out experiments to find the relationship between force and extension for a single spring, springs in series or parallel, rubber band, polythene strip, etc.

Plenary
Go over Hooke’s Law (F=kx)

Individuals

Resources:
single spring, springs in series or parallel, rubber band, polythene strip, 100g mass sets, stands, bosses, clamps, 50 cm rulers

Homework:
Lesson 31 qs

7

Evaluation:


 






Ref: G481.32

Title: Strain Energy

Group

Date

Period

Room

Objectives – by the end of the session pupils should be able to:
(d) determine the area under a force against extension (or compression) graph to find the work done by the force;
(e) select and use the equations for elastic potential energy
E = 1/2Fx and
E = ½ kx2

Keywords:
Strain
Tensile
Compressive
Potential energy

Follows from:
Links to:

Starter Activity
demo a catapult. Ask: how can I find the energy stored in it (find grav potential of object fired, assume all converted from strain into grav) or similarly with ke. try to do with light gates. remind of hooke’s law and graph. Can work out energy from average force x distance (since energy = Fx)

Development Activity
Load extension experiment for an elastic band catapult.

Plenary Activity

Did our experiments match up with each other? why not/why? Evaluate.

Individuals

Resources:
Elastic bands (catapults), 50g mass sets, goggles, metre rules, stands and clamps.

Homework:
Lesson 32 HW sheet

8

Evaluation:

 


 






Ref: G481.33

Title: Young Modulus

Group

Date

Period

Room

Objectives – by the end of the session pupils should be able to:
(f) define and use the terms stress, strain, Young modulus and ultimate tensile strength (breaking stress);
(g) describe an experiment to determine the Young modulus of a metal in the form of a wire;

Keywords:
stress, strain, Young modulus and ultimate tensile strength (breaking stress)

Follows from:
Links to:

Starter Activity
Define stress and strain and relationship to the Young modulus - ppt

Development Activity
Use Searle’s Apparatus in Alan Beers (SC06) room because of beam.

 

 

Plenary Activity
Draw out and describe experiment from memory – then give out print out from notes. Emphasise the need to learn this practical for the exam.

Individuals

Resources:
Wire on beam, micrometer, Kilo mass set, 100g mass set, Searle’s Apparatus, metre rule. 0.08 mm stainless steel (or similar), safety spectacles

Homework:
Find the Value of Young Modulus for steel.
Lesson 33 questions

9Eye protection in case of wire snapping. Soft landing area.

Evaluation:

 

 






Ref: G481.34

Title: Material properties

Group

Date

Period

Room

Objectives – by the end of the session pupils should be able to:
(h) define the terms elastic deformation and plastic deformation of a material;
(i) describe the shapes of the stress against strain graphs for typical ductile, brittle and polymeric materials.

Keywords:
elastic deformation and plastic deformation
ductile, brittle and polymeric materials

Follows from:
Links to:

Starter Activity
Define terms: Ductile, Brittle, Polymeric, Strong, Stiff, Tough, Hard. They need to concentrate as they will have a quiz at the end.

Development Activity
powerpoint
Give out a load of sweets that have to be defined by the words. (see if Ray can help you out with some cheap sweets from his daughter)
Draw some graphs of ductile, brittle and polymeric materials.

 

 

Plenary Activity
quiz students on definitionss.

Individuals

Resources:
Sweets, trays, hammers,

Homework:
Lesson 34 questions

10Eye protection in case of sweet splinters in the eye.

Evaluation:

 






Ref: G481.35

Title: 1.3 Work and Energy Test

Group

Date

Period

Room

Objectives – by the end of the session pupils should be able to:
Assess their knowledge and understanding

Keywords:

Follows from:
Links to:

Starter Activity - test

Development Activity

 

 

Plenary Activity
Go through test

Individuals

Resources:
1.3 Work and Energy Test

Homework:

11

Evaluation:

 

 

 

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