List things around them that use the principle of the lever State what a lever can do Identify load, force and fulcrum of the lever Classify lever Explain what is meant by the moment of force Solve problems related to levers
What is Lever ?
Lever is a) A si simp mple le ma mach chin ine e b) Enable Enabless smal smalll effor effortt to ove overco rcome me a heavy load c) Can be us used ed to to lift lift hea heavy vy obj object ectss d) Ma Make kess wor work k eas easie ierr A lever is a simple machine which turns about a fixed point called the FULCRUM (F ) when a force called the EFFORT E FFORT (E ) is applied to overcome a resisting force
Types of Simple Machines
Wedge Wheel and axle
Lever
6 types of simple machines
Screw Pulley
Inclined plane
What is Lever ?
A lever has 3 parts a)Fulcrum (F) – the turning point or pivot b)Effort (E) – the force applied to overcome a resisting force called the load c)Load (L) – the resisting force exerted by an object
Simple Machines E F
L
E
L
F E L L
E F
E
E
L
L L E
F
What is Lever ?
Lever can be classified into a) 1st class b)
2nd class
c)
3rd class
Classes of Levers
Lever
A lever is a simple machine which turns about a fixed point called the FULCRUM (F ) when a force called the EFFORT (E ) is applied to overcome a resisting force known as the LOAD (L ). ).
3 classes of levers
First class
Second class
Third class
1st class
First Class Lever
E F
First class lever
Common devices
Common characteristics
Relative position of , E and L F
F between E and L
L
•
•
•
Small force is used to move a large load Effort moves through a longer distance than the load Effort is further from the fulcrum than the load
•
Claw hammer
•
Pliers
•
Scissors
•
Crowbar
2nd class
Second Class Lever
E
F
Second class lever
Relative position of , E and L F
L between F and E
L
Common devices
Common characteristics
•
•
•
Small force is used to move a large load Effort moves through a longer distance than the load Effort is further from the fulcrum than the load
•
Wheelbarrow
•
Bottle opener
•
Paper cutter
•
Nutcracker
Third Class Lever
3rd class
E
F
Third class lever
Common devices
Common characteristics
Relative position of , E and L F
E between F and L
L
•
•
•
Large force is used to move a small load Load moves through a longer distance than the effort Load is further from the fulcrum than the effort
•
Fishing rod
•
Broom
•
Ice tongs
•
Human arm
1st class
E F
=
L
F
E
=
F
L
E
=
F
E
L
L
2nd class
E
F L
3rd class
E
F L
F E
L
E
F L
F
E
E
L
L L E
F
E
E
L
F
L
F
E
L
E
E
F
F
L L
What is the Moment of a Force? When we loosen a bolt using a spanner, a force that is applied has a turning effect on the spanner. This turning effect of force is known as the moment of force Spanner
Spanner P
Q
Force 18 cm
Force 7 cm
a) It is is easier easier to loose loosen n the the bolt bolt if you hold the span spanner ner at position P than Q because the turning effect is greater. b) It is is also also easier easier to to loosen loosen the the bolt bolt if a larger larger force force is is applie applied d at P to cause a greater turning effect.
What is the Moment of a Force? •
•
The moment of a force is the turning effect of the force The moment of a force is defined as:
Moment of a force (N m)
= Force (N) x
The moment of a force can be increased by
Perpendicular distance from the pivot to the force (m)
Increasing the size of the force Applying the force at a further distance dist ance from the pivo pivott
To Calculate the Moment of a Force
Opening a door
0.6 m
4N
Moment of a force (N m)
= Force (N) x = 4N =
x
2.4 N m
Perpendicular distance from the pivot to the force (m)
