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Work and Power

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Work and Power

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Work

When a force acts upon an object to cause a displacement of the object

Mathematically, work can be expressed by the following equation.

Scenario A: A force acts rightward upon an object as it is displaced rightward. In such an instance, the force vector and the displacement vector are in the same direction. Thus, the angle between F and d is 0 degrees.

Scenario B: A force acts leftward upon an object that is displaced rightward. In such an instance, the force vector and the displacement vector are in the opposite direction. Thus, the angle between F and d is 180 degrees.

Scenario C: A force acts upward on an object as it is displaced rightward. In such an instance, the force vector and the displacement vector are at right angles to each other. Thus, the angle between F and d is 90

To Do Work, Forces Must Cause Displacements!

- If force is 5 newtons and the object is moved 10 meters, how much work has been done?
- Work = Force x Distance
- Work = 5 N x 10 m
- Work = 50 Nm

- Work can be positive or negative.
- The distance and direction through which an object moves is called its displacement.
- If the force and movement are in the same direction, the work is positive.
- If the force and movement are in opposite directions, the work is negative.

- Machines are designed to convert energy or work input to work output.
- Efficiency = output work / input work
- Percent efficiency = output work / input work x 100%

- If output work is 20 and input work is 40, what is the efficiency?
- What is the percent efficiency?
- Efficiency = Output / Input
- Efficiency = 20 / 40
- Efficiency = .50
- Percent Efficiency= Efficiency x 100%
- Percent Efficiency = .50 x 100%
- Percent Efficiency = 50%

- HOW FAST work is being done
- The same amount of work done faster will produce more power
- Power is the rate at which work is done
- Power is the amount of work done in a certain amount of time

POWER

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MEASURED IN

SECONDS (s)

MEASURED IN

WATTS (W)

MEASURED IN

JOULES (J)

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