Pulleys Investigation
Pulleys are simple machines, which can be used to redirect or reduce the _________ needed to lift an object. They are used in cranes, lifts (elevators) and
factories.
The energy transferred in lifting the mass is the change in ___________
__________ _____. If we want to lift a 100N mass 10cm (0.1m), then:
Change in GPE (J) = __________ (N) x __________ (m)
= ______ x ______
= ____ Joules
 this is the energy needed to lift the mass
10cm.
In the diagrams below, the same mass is lifted the same height, needing 10J of
energy.
However the _______ needed can be changed depending on the _______ of pulleys
used:
Pulley systems use the fact that:
E______ T______________ to GPE (___) = W______ d______ by person
pulling (___)
And we know that:
Work Done = F________ x D____________
We compare the number of pulleys to the Pulling Force needed and the Distance
Pulled
Number of pulleys
Pulling Force (N)
Distance Pulled (m)
Work done (J)
Energy transferred
(J)
Graph of Results:
1
2
3
4
How force changes when more pulleys are
used
120
Pulling Force (N)
100
80
60
40
20
0
0
1
2
3
4
5
6
7
Number of pulleys
Describe the relationship shown by the graph:
As the number of pulleys increases, the pulling force _____________
However the W___ D____ is always the same (Force x distance always equals 10
Joules).
This means that the person has to use the same e________ to lift the mass 10cm,
but if they want to use a smaller f________, they have to pull the string a bigger
d___________.
Can you use the graph to work out how much force would be needed if there were:
a) 5 pulleys?
b) 7 pulleys?
Show your working on the graph.
Pulleys Investigation
Pulleys are simple machines, which can be used to redirect or reduce the force
needed to lift an object. They are used in cranes, lifts (elevators) and factories.
The energy transferred in lifting the mass is the change in Gravitational Potential
Energy. If we want to lift a 100N mass 10cm (0.1m), then:
Change in GPE (J) = weight (N) x height (m)
= 100 x 0.1
= 10 Joules
 this is the energy needed to lift the mass
10cm.
In the diagrams below, the same mass is lifted the same height, needing 10J of
energy.
However the Force needed can be changed depending on the number of pulleys
used:
Pulley systems use the fact that:
Energy Transferred to GPE (J) = Work done by person pulling (J)
And we know that:
Work Done = Force x Distance
We compare the number of pulleys to the Pulling Force needed and the Distance
Pulled
Number of pulleys
Pulling Force (N)
Distance Pulled (m)
Work done (J)
1
100
0.1
100 X 0.1 =
10
10
Energy transferred
(J)
Graph of Results:
2
50
0.2
50 X 0.2 =
10
10
3
33.3
0.3
33.3 X 0.3 =
10
10
4
25
0.4
25 X 0.4 =
10
10
How force changes when more pulleys are
used
120
Pulling Force (N)
100
80
60
40
20
0
0
1
2
3
4
5
Number of pulleys
Describe the relationship shown by the graph:
As the number of pulleys increases, the pulling force decreases
6
7
However the Work Done is always the same (Force x distance always equals 10
Joules).
This means that the person has to use the same energy to lift the mass 10cm, but if
they want to use a smaller force, they have to pull the string a bigger distance.
Can you use the graph to work out how much force would be needed if there were:
a) 5 pulleys?
b) 7 pulleys?
Show your working on the graph.