Work and Work and PowerPower

AssignmentAssignment

I will number you into groups.I will number you into groups.

You will be working in chapter 8 of You will be working in chapter 8 of the book.the book.

Your group number will represent Your group number will represent your section of the chapter. your section of the chapter.

ExpectationsExpectations

You will be presenting your section to You will be presenting your section to class. class.

The method of presentation is your The method of presentation is your choice. (notes, demonstrations, vocab choice. (notes, demonstrations, vocab game…) game…)

Your group will also generate 5 test Your group will also generate 5 test questions (multiple guess / calculations)questions (multiple guess / calculations)

WorkWorkWork – a force applied over a Work – a force applied over a distancedistance

W= F(d)W= F(d)

units: F=Newton d=meterunits: F=Newton d=meterW= JoulesW= Joules

W = F x dW = F x dTherefore:Therefore:

You must have MOTION in order to You must have MOTION in order to have work… something has to have work… something has to change positionchange position

PowerPowerPower – the rate at which work Power – the rate at which work is doneis done

Power = Work/timePower = Work/time

Unit is Watt (joule/second)Unit is Watt (joule/second)

Example ProblemsExample ProblemsIf a 450 N boulder is If a 450 N boulder is dropped 2.4 m in 25 dropped 2.4 m in 25 seconds, how much power seconds, how much power is exerted on the object?is exerted on the object?

Example ProblemsExample Problems

How much work is done by a toy How much work is done by a toy car with an applied force of 12 car with an applied force of 12 N which is moved for 39 m?N which is moved for 39 m?

The weight lifter lifted a mass of 100 kg (barbell) over her head in 5.21 seconds. Approximately how much power did she generate in raising the barbell?

A mechanic used a hydraulic lift to raise a 12,054 N car 1.89 m above the floor of a garage. It took 4.75 s to raise the car. What was the power output of the lift?

Example ProblemsExample Problems