0
Upcoming SlideShare
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×
Saving this for later? Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime – even offline.
Standard text messaging rates apply

# Ppt Work

2,278

Published on

1 Like
Statistics
Notes
• Full Name
Comment goes here.

Are you sure you want to Yes No
• Be the first to comment

Views
Total Views
2,278
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
87
0
Likes
1
Embeds 0
No embeds

No notes for slide

### Transcript

• 1. Work & Machines
• 2. What is work?
• If you push or pull something, that is NOT work.
• Work is the transfer of energy that happens when a force makes an object move .
• Remember – force is a push or a pull on an object
• Key - for work to be done, the object has to move .
• 3. Doing Work
• Two things have to happen in order to consider it work…
• The object has to move
• The motion of the object has to be in the direction the force was applied.
• 4. Doing Work Example
• The bell rings and you need the books under your desk.
• Lifting up the book is doing work…why?
• The books move and…
• There is a force applied, by your arms, in the direction that the books move.
• 5. Doing Work Example
• Your arms are doing the work.
• Now that they are in your hands, you start to walk with them…
• It is now your legs that are doing the work to move you and your books, not your arms.
• 6. Work and Energy
• When work is done, energy is always transferred.
• Think about carrying a box with your kid brother up the stairs. When you are done, your arms will be sore.
• Remember – when you increase the height of an object you increase its potential energy.
• 7. Work and Energy
• So, by taking the box-n-brother up the stairs, you have increased its height, therefore, increasing its potential energy and you transferred energy to it.
• 8. Work and Energy
• Remember – Energy is the ability to cause change.
• AKA – Energy is the ability to do work.
• If something has energy, it can transfer energy to something else.
• 9. Work and Energy
• When you do work on something, you increase its energy.
• IF you do work on something, you decrease your energy.
• Energy is always transferred from the object that is doing the work to the object that has the work done on it.
• 10. Calculating Work
• Would you do more work if you lifted the books from the floor to your waist or from the floor to over your head?
• You do more work when you exert a greater force and when you move an object a greater distance.
• 11. Calculating Work
• The amount of work done depends on two things.
• The amount of force exerted
• The distance the object is moved
• 12. Calculating Work
• When a force is exerted and an object moves in the direction of the force, the amount of work done can be calculated…
• Work = Force x distance
• W=Fd
• 13. Calculating Work
• If Maria applies a force of 25N to a baseball for a distance of .1m, how much work did she do?
• W = ?
• F = 25N
• d = .1 m
Remember - Newton x meter = Joule & Work is always measured in Joules
• W=Fxd
• W = 25 N x .1m
• W = 2.5 J
• 14. Calculating Work
• Force is measured in
• Newtons (N)
• distance is measured in
• meters (m)
• Newton (N) times meters (m) = Joule
• Work, like energy is measured in
• Joules (J)
• One joule is about the amount of work required to lift a baseball a vertical distance of 0.7m
• 15. When is work done?
• Push a book across a table a distance of 1m.
• The distance you use to calculate the work you did is how far the book moved while the force is being applied , or while your hand is in touching the book.
• The distance in the formula, W=Fd, is the distance that your hand was in contact with the book