# 27114-work-done (1)

```Work done
Starter
What unit is mass measured in?
Mass is measured in kg
What unit is weight measured in?
Weight is measured in newtons, N
What unit is energy measured in?
Energy is measured in joules, J
Challenge: What causes weight to be different
to mass?
Weight is caused by the interaction between mass and gravity.
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Learning objectives
Identify situations where work is being done.
Describe the work done on an object by using the equation.
Explain the relationship between work done and force using
data.
Apply your understanding of the work done equation to
rearrange it.
calculate the distance and accelerating object travels.
Keywords:
gravity joules newton displacement
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LO: Identify situations where work is being
done
What have these images got in common?
Think, pair, share
Decide what you think
the images have in
common, and be
to the class.
W=Fxs
W = work done (J)
F = force (N)
s = distance moved (m)
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You now know that
the work done, is the
product of the force
(in newtons) and the
distance the object is
moved (in meters).
Can you rearrange
the equation to make
the force (F) and
distance moved (s)
the subject of the
formula to make two
more equations?
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W=Fxs
W = work done (J)
F = force (N)
s = distance moved (m)
Hint!
F=
s=
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We will use
these equations
later on to find
how much work
is done, the
force applied or
the distance an
object has
moved!
W=Fxs
F = W &divide;s
s=W&divide;F
W = work done (J)
F = force (N)
s = distance moved (m)
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27114
5
Look at the cartoons below.
Which of the situations require work to be done?
Remember, for work to be done, a force must be
applied to move an object.
30
Freya
J ofpushes
work isa
done
15 N trolley
to move2 m
the
to the
trolley.
sweets.
No
250work
N Billy
(0 J)
waits
is
being
as
for thedone
green
Billy
man is
atnot
the
moving.
traffic lights.
60
J of
work
Oleg
lifts
a is
done
to move
30 N box,
2m
the
frombox
theoff the
ground.
ground.
Challenge - for each situation, calculate the work done.
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27114
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Learning objectives
Identify situations where work is being done.
Describe the work done on an object by using the
equation.
Explain the relationship between work done and force using
data.
Apply your understanding of the work done equation to
rearrange it.
F=ma to calculate the distance and accelerating object
travels.
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27114
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Use the equation for work done to calculate how much work is
being done in each of these situations.
Ardel pushes the lawn
mower 2 metres and applies
a 5 N force.
How much work does Ardel
do?
The rugby team pushes
another team
with a 10 N force 2 meters.
What is the work done?
Emily does 60 J of work
rolling a log of wood 2 m
through the woods.
What is the mass of the
wooden log?
Challenge
A car does 2.5 MJ of work to
move along a motorway. If
the engine drives with a
force of 250 000 N, how far
does the car travel?
10 m
10 J
30 kg
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20 J
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Crorcet the sicecne and the garmamr
work done and energy transferred are measured in Newtons (N).
The work done on a object can be calculator if the work and
distance moved are known.
Work and force and distance
You should no, and be able to use, the relationship between work
done and force applied and distance moved.
The equation
This equation shows the relationship between work done, force
applied and distance moved:
work done (seconds, s) = force (seconds, s) &times; distance (second,
s)
The distance involved is the distance moved in the One Direction of
the applied force.
&copy; www.teachitscience.co.uk 2017
27114
9
Crorcet the sicecne and the garmamr
work done and energy transferred are measured in Newtons (N).
The work done on a object can be calculator if the work and
distance moved are known.
Work and force and distance
You should no, and be able to use, the relationship between work
done and force applied and distance moved.
The equation
This equation shows the relationship between work done, force
applied and distance moved:
work done (seconds, s) = force (seconds, s) &times; distance (second,
s)
The distance involved is the distance moved in the One Direction
of the applied force.
&copy; www.teachitscience.co.uk 2017
27114
10
Correct all answers in green pen shown below!
Correct the science and the grammar
Work done and energy transferred are measured in joules (J).
The work done on an object can be calculated if the force and
distance moved are known.
Work, force and distance
You should know, and be able to use, the relationship between
work done, force applied and distance moved.
The equation
This equation shows the relationship between work done, force
applied and distance moved:
work done (joules, j) = force (newtons, N) &times; distance (metres,
m)
The distance involved is the distance moved in the direction of the
applied force.
&copy; www.teachitscience.co.uk 2017
27114
11
Learning objectives
Identify situations where work is being done.
Describe the work done on an object by using the
equation.
Explain the relationship between work done and force
using data.
Apply your understanding of the work done equation to
rearrange it.
calculate the distance and accelerating object travels.
&copy; www.teachitscience.co.uk 2017
27114
12
LO: Explain the relationship between work done
and force by using data
Use the work sheet.
&copy; www.teachitscience.co.uk 2017
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Learning objectives
Identify situations where work is being done.
Describe the work done on an object by using the
equation.
Explain the relationship between work done and force
using data.
Apply your understanding of the work done equation to
rearrange it.
calculate the distance and accelerating object travels.
&copy; www.teachitscience.co.uk 2017
27114
14
Now you have shown you can use the work done equation,
complete these more difficult questions!
1. Kiran uses 2.5 kJ of energy by moving a chair 56 cm. What is
the weight of the chair?
4 464 N (4.5 kN)
2. What is the work done to a car if a force of 9 kN is applied over
a distance of 7 km?
63 000 000 J (63 MJ)
Challenge: A car has a mass of 1000 kg (10 000 N), and accelerates
at a constant rate of 3 m/s2. What is the force applied to the
3000 N (3kN)
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1.
The energy of a moving object is called its
_______
kinetic energy store.
2. When an object falls, the energy in its
_____________
potential
gravitational ______________
energy store decreases.
force causes movement of an object,
3. When a ________
_____
work is done.
4. Lifting an object increases the energy in its
_____________
gravitational __________
potential energy store.
5. When an object is lifted to a higher position above
work is done by the lifting force
the ground, _______
against the gravitational force acting on the object
(its ________).
weight
weight
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work
Keywords:
force gravitational
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potential
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6. Using the equation
work done by a force (J) =
force (N)
&times;
distance moved by the force (m)
Calculate the work done pushing the book with force of 5 N along a
desk for a distance of 0.8 m.
7. Using the equation
change in GPE (J) = weight (N)
&times; vertical height difference (m)
i) The book has a weight of 10 N and is lifted from the desk a
height of 0.7 m and is placed on a shelf. Calculate the change
in GPE for this book.
ii) What is the minimum amount of work that has been done in
lifting the book.
iii) The book then falls to the ground from the shelf (not back on to
the desk). If the book loses If the book loses 15 J of GPE in
the fall, how high is shelf above the floor?
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calculate the distance and accelerating object travels.
Challenge
The book has a mass of 1 kg, and accelerates to
the ground at a rate of 10 m/s2. If the work
done by gravity for the book to fall to the
Use the equation F=ma and the work done
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Learning objectives
Identify situations where work is being done.
Describe the work done on an object by using the
equation.
Explain the relationship between work done and force
using data.
Apply your understanding of the work done equation to
rearrange it.