Work and Power
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Work and Power. K. L. What have you learned about Work and Power ?. What do you know about Work and Power?. What do you want to know about Work and Power?. W. Work. When a force acts upon an object to cause a displacement of the object.

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Work and Power

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Work and power

Work and Power

K

L

What have you learned about Work and Power?

What do you know about Work and Power?

What do you want to know about Work and Power?

W


Work and power

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


Work and power

To Do Work, Forces Must Cause Displacements!


Work and power

  • 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 and power

  • 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.


Work energy theorem

Work Energy Theorem


Work and power

  • 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%


Work and power

  • 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%


Power

POWER

  • 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


Power1

POWER

WORK

/

TIME

=

MEASURED IN

SECONDS (s)

MEASURED IN

WATTS (W)

MEASURED IN

JOULES (J)

WORK

POWER

x

TIME

=

TIME

WORK

/

POWER

=

POWER


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