Work, Power and Simple Machines
Work Distance 10 m Force 40 N W = F * d = 40 N * 10 m = 400 Joules Force acting through a distance
Work l Force must be in same direction as distance Force Distance
Work l Force must be in same direction as distance Force Distance There is no work being done on the farmer
Power How fast (or the rate) Work is done P = W/t 400 J/1 sec = 400 watts 400 J/5 sec = 80 watts
How do machines make work easier? Work InWork Out DistanceForce DistanceForce DistanceForce DistanceForce Increase F MA>1 Increase D MA<1 Change direction of F MA=1
Even though machines make work easier, they cannot change the amount of work Work InputWork Output F effort *distanceF resistance *distance Work Input is always greater than Work Output due to Friction
Even though machines make work easier, % Efficiency = Work Output / Work Input *100 Work InputWork Output F effort *distanceF resistance *distance Work Input is always greater than Work Output due to Friction 10N*5m= 50J 20N*2m= 40J
Even though machines make work easier, % Efficiency = (40 J / 50 J) = 0.8 Work InputWork Output F effort *distanceF resistance *distance Work Input is always greater than Work Output due to Friction 10N*5m= 50J 20N*2m= 40J
Even though machines make work easier, % Efficiency = (40 J / 50 J) = 0.8 *100 =80% Work InputWork Output F effort *distanceF resistance *distance Work Input is always greater than Work Output due to Friction 10N*5m= 50J 20N*2m= 40J
Inclined Plane A slanted surface used to raise an object
Inclined Plane
5 N
Inclined Plane l Decreases the size of the effort force 5 N 4 N
Inclined Plane l Decreases the size of the effort force 5 N 4 N
Inclined Plane l Decreases the size of the effort force l Increases the distance 5 N 4 N
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 Mechanical Advantage = resistance F / effort F = 2 N
1st class Mechanical Advantage = resistance F / effort F = 2/2 = 1 2 N
2nd class Mechanical Advantage = resistance F / effort F = 2 N 1 N
2nd class Mechanical Advantage = resistance F / effort F = 2/1 = 2 2 N 1 N
3rd class Mechanical Advantage = resistance F / effort F 2 N 3 N
3rd class Mechanical Advantage = resistance F / effort F = 2/3 = N 3 N
5 N Pulleys Fixed Movable
5 N Pulleys 5 N 2.5 N Fixed Movable MA = 5/5=1 MA = 5/2.5 =2
5 N Pulleys 5 N 2.5 N Resistance distance = Effort distance Resistance distance = 1/2 Effort distance
Wheel and Axle l Two circular objects of different size l The wheel always moves a greater distance than the axle
Wheel and Axle l Wheel : Large Distance, Small Force l Axle : Small Distance, Large Force
Compound Machine Corkscrew l Inclined Plane? l Wedge? l Screw? l Lever? l Pulley? l Wheel and Axle?
Compound Machine Corkscrew l Inclined Plane l Wedge l Screw l Lever l Pulley l Wheel and Axle
Compound Machine Drill l Inclined Plane? l Wedge? l Screw? l Lever? l Pulley? l Wheel and Axle?
Compound Machine Drill l Inclined Plane l Wedge l Screw l Lever l Pulley l Wheel and Axle
Compound Machine Jack l Inclined Plane? l Wedge? l Screw? l Lever? l Pulley? l Wheel and Axle?
Compound Machine Jack l Inclined Plane l Wedge l Screw l Lever l Pulley l Wheel and Axle