AIM: How do we define and calculate work and power?

OBJ: Given notes and activity sheet SWBAT define and calculate work and power with 70% accuracy

DN: Distribute

ACT:

HW:

What is Work?Work occurs when you exert a force on an object that causes the object to move some distance. In addition, the object must move in the same direction in which the force is exerted.More simply put: work unit = joule (J); where 1J = 1Nm

Work(J) = Force (N) X Distance (m)Remember: work is done on an object when:1] An object moves a distance.2] Force is exerted on the object, and3] The force and motion direction are parallel (same). Carrying an object = no work

Work Problem

How much work is done given a force of 20N and a distance of 10 meters?

W = F x DW = 20N x 10mW = 200 Nm = 200J

What is Power?Power: the rate at which work is done.

Power = Work (J) = Force (N) x Distance m)Time (s) Time (s)

Power Unit: J/s or Watt (W), where 1W = 1 J/sOne kilowatt (kW) = 1,000 WattsOne horsepower = 746 watts

Power ProblemA tow truck exerts a force of 11,000N to pull a car out of a ditch. It moves the car a distance of 5 m is 25 seconds. What is the power of the tow truck?

Power = Force x DistanceTime

Power = 11,000N x 5m = 55,000Nm = 2,200J/s25s 25s

= 2,200 W = 2.9 hp