Work and Power

Work and Power

​Force must act in the same direction as the 

object moves

Force:

The product of force and distance

(W=FxD

Definition: ​

Work​

​When there is NO movement: the direction of the force and the direction of the movement are different.

When Work is NOT Done​:

Object moves in the direction of the force.​

​When is Work Done:

Work Equation: ​

​Work: Joules

Force: Newtons

Distance: Meters ​

Multiple Choice

Fred kicks a ball with a force of 20N to George, who is 5M away.

How much work was done to the ball?

• 25 J

• 15 J

• 100 J

• 4 J

Multiple Choice

 

If you push a cart with a force of 60 N for 2 m... how much work have you done?

• 30 J

• 62 J

• 120 J

• 15 J

Power

The rate of doing work​

(Power=Work/Time)​

Work-Joules

Power- Watt

Time- Seconds​

​

​

Multiple Choice

How much time is needed to produce 720 Joules of work if 90 watts of power is used? 

• 0.125 s

• 8 s

• 64800 s

• 80 s

Multiple Choice

You do 90 joules of work in 30 seconds. How much power have you generated?

• 30 W

• 3 W

• 120 W

• 270 W

​Machine

Something that changes a force; makes work easier to do​

​Simple Machines

​There are 6 simple Machines:

• Lever

• Wheel and axle

• Pulley

• Inclined plane

• Wedge

• Screw

​A simple machine is a mechanical device that changes the direction or magnitude of a force. In general, they can be defined as the simplest mechanisms that use mechanical advantage (also called leverage) to multiply force.

​Compound Machine

Two or more simple machines that operate together

​Input

The amount of force, distance, or work made by the person while using a machine

​Output

The amount of force, distance, or work made by a machine doing something

Efficiency

The percentage of work input that becomes work output, less than 100% due to friction

The mechanical advantage of a machine in the absence of friction

​Ideal Mechanical Advantage

The mechanical advantage of a machine by measuring the ratio of output force to input force

​

​Actual Mechanical Advantage

Mechanical Advantage

Multiple Choice

Something that changes a force; makes work easier to do

• Efficiency

• Machine

• Input

• Output

Multiple Choice

The amount of force, distance, or work made by the person while using a machine

• Input

• Output

• Machine

• Effeciency

Multiple Choice

The amount of force, distance, or work made by a machine doing something

• Input

• Output

• Machine

• Effeciency

Multiple Choice

The percentage of work input that becomes work output, less than 100% due to friction

• Input

• Output

• Machine

• Effeciency

Multiple Choice

The mechanical advantage of a machine by measuring the ratio of output force to input force

• Actual Mechanical Advantage

• Ideal Mechanical Advantage

• Efficiency

• Compound Machine

Multiple Choice

The mechanical advantage of a machine in the absence of friction

• Actual Mechanical Advantage

• Ideal Mechanical Advantage

• Efficiency

• Compound Machine