Post on 02-Jan-2016
Chapter 6 Section 1 Work and Machines
Define work:______________________________________________________________________________________________________________________________What 2 conditions apply to work?1.__________________________________________________________________________________2. __________________________________________________________________________________
• Recall that energy is the ability to cause change.
• Another way to think of energy is that energy is the ability to do work.
• If something has energy, it can transfer energy to another object by doing work on that object.
What does the amount of work depend on?__________________________________________________________________________________________What is the formula for work?
Suppose you push a box of books up a 10m ramp. You apply a force of 10N and it takes you 20s to push the box. How much work is done pushing the box? Remember W=Fd
• Suppose you give a book a push and it slides along a table for a distance of 1 m before it comes to a stop. Did you do work the entire time?
________________________________________________________________________________________________________
What is power?__________________________________________________________________________________What is the formula for power?
NOTICE – The SI unit for power is the Watt (J/s) **Because the watt is a small unit, power often is expressed in kilowatts - One kilowatt (kW) equals 1,000 W
Suppose you push a box of books up a 10m ramp. You apply a force of 10N and it takes you 20s to push the box. How much work is done pushing the box? In the work problem you found that W= 100 JNow use the Power formula to calculate how much power you used. Remember P=W/t
Power and Energy – making connections• Power is also the rate at which
energy is transferred.
• The power involved can be calculated:
NOTICE – Power is Joules/seconds with both work and energy
Suppose a light bulb changes electrical energy into light and heat at a rate of 100J in 2s. How many watts of power does the light bulb have?Use P=E/t
Section CheckSection Check
__________ is the transfer of energy that occurs when a force makes an object move.
A. ConversionB. EnergizationC. PowerD. Work
11Question 1
Section CheckSection Check
The amount of work done depends on what two things?
11Question 2
Section CheckSection Check
Which of the following equations can be used to calculate power?
A. W = F/dB. P =WtC. t = W/PD. P = t/W
11Question 3