Transcript Work, Power and Simple Machines

Work, Power and Simple
Machines
Force
40 N
Work
Force acting through a
distance
Distance
10 m
W=F*d
= 40 N * 10 m = 400 Joules
Work

Force must be in same direction
as distance
Force
Distance
Work

Force must be in same direction
as distance
Force
There is no work
being done on the
farmer
Distance
Power
400 J/1 sec = 400 watts 400 J/5 sec = 80 watts
How fast (or the rate) Work
is done
P = W/t
How do machines make
work easier?
Work In
Work Out
Increase F
ForceDistance MA>1
Force Distance
Force Distance
Increase D
MA<1
Change
direction of F
Force Distance
MA=1
Even though machines
make work easier,
they cannot change the amount of work
Work Input
Work Output
Feffort*distance
Fresistance*distance
Work Input is always greater than Work Output due to
Friction
Work Even
Input is always
greater than
Work Output due to
though
machines
Frictioneasier,
make work
% Efficiency = Work Output / Work Input *100
Work Input
Feffort*distance
10N*5m=
50J
Work Output
Fresistance*distance
20N*2m=
40J
Work Even
Input is always
greater than
Work Output due to
though
machines
Frictioneasier,
make work
% Efficiency =
Work Input
Feffort*distance
10N*5m=
50J
(40 J / 50 J)
= 0.8
Work Output
Fresistance*distance
20N*2m=
40J
Work Even
Input is always
greater than
Work Output due to
though
machines
Frictioneasier,
make work
% Efficiency =
Work Input
Feffort*distance
10N*5m=
50J
(40 J / 50 J)
= 0.8 *100
=
80%
Work Output
Fresistance*distance
20N*2m=
40J
Inclined Plane
A slanted surface used to
raise an object
Inclined Plane
Inclined Plane
5N
Inclined Plane
4N
5N
5N
Decreases
the size of the
effort force
Inclined Plane
4N
5 N5 N
Decreases
the size of the
effort force
Inclined Plane
5N
4N
5N
Decreases
the size of the
effort force
Increases the distance
Wedge
An inclined plane that
moves
Wedge
An inclined plane that
moves
Wedge
An inclined plane that
moves
Wedge
An inclined plane that
moves
Wedge
An inclined plane that
moves
Wedge
An inclined plane that
moves
Wedge
As a wedge moves
through an object to
be cut,
Wedge
A small effort force
Wedge
A small effort force
Is able to overcome
Wedge
A small effort force
Is able to overcome
A large resistance force
Wedge
A small effort force
Is able to overcome
A large resistance force
Wedge
How can the
mechanical advantage
be increased?
Wedge
How can the
mechanical advantage
be increased?
Reduce the effort force by
decreasing the angle
Screw
An inclined plane wrapped
around a central bar or
cylinder to form a spiral
How fast (or the rate) Work
is done
1st class
2N
2N
Mechanical Advantage =
resistance F / effort F =
1st class
2N
2N
Mechanical Advantage =
resistance F / effort F =
2/2 = 1
2nd class
1N
2N
Mechanical Advantage =
resistance F / effort F =
2nd class
1N
2N
Mechanical Advantage =
resistance F / effort F =
2/1 = 2
3rd class
3N
2N
Mechanical
Advantage =
resistance F / effort F
3rd class
3N
2N
Mechanical
Advantage =
resistance F / effort F
= 2/3 = 0.66
Pulleys
Fixed
Movable
Pulleys
Fixed
MA = 5/2.5 =2
2.5 N
2.5 N
5N
MA = 5/5=1
Movable
Pulleys
2.5 N
2.5 N
5N
Resistance distance =
Effort distance
Resistance distance =
1/2 Effort distance
Wheel and Axle


Two circular
objects of
different size
The wheel
always moves a
greater distance
than the axle
Wheel and Axle


Wheel : Large Distance, Small
Force
Axle : Small Distance, Large
Force
Compound Machine
Corkscrew






Inclined Plane?
Wedge?
Screw?
Lever?
Pulley?
Wheel and Axle?
Compound Machine
Corkscrew






Inclined Plane
Wedge
Screw
Lever
Pulley
Wheel and Axle
Compound Machine
Drill






Inclined Plane?
Wedge?
Screw?
Lever?
Pulley?
Wheel and Axle?
Compound Machine
Drill






Inclined Plane
Wedge
Screw
Lever
Pulley
Wheel and Axle
Compound Machine
Jack






Inclined Plane?
Wedge?
Screw?
Lever?
Pulley?
Wheel and Axle?
Compound Machine
Jack






Inclined Plane
Wedge
Screw
Lever
Pulley
Wheel and Axle