1. Chapter 6 Section 1 Work and Machines

2. Define work: __________________________________________ What 2 conditions apply to work? 1.________________________________________ __________________________________________ 2. ________________________________________ __________________________________________

3. 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.

4. What does the amount of work depend on?______________________________ ______________________________ What is the formula for work?

5. 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

6. 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? ____________________________________ __________________________________ __________________________________

7. 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

8. 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 J Now use the Power formula to calculate how much power you used. Remember P=W/t

9. 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

10. 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

11. Section Check __________ is the transfer of energy that occurs when a force makes an object move. A. Conversion B. Energization C. Power D. Work 1 1 Question 1

12. Section Check The amount of work done depends on what two things? 1 1 Question 2

13. Section Check Which of the following equations can be used to calculate power? A. W = F/d B. P =Wt C. t = W/P D. P = t/W 1 1 Question 3