1 / 27

Today’s lesson

Today’s lesson. Learn what “work” is! Learn how to calculate work See who can do the most work! If we have time we will look at power. A reminder. Energy cannot be made or destroyed, only transformed (changed). Energy is measured in Joules. That’s me!. Work.

kueng
Download Presentation

Today’s lesson

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Today’s lesson • Learn what “work” is! • Learn how to calculate work • See who can do the most work! • If we have time we will look at power.

  2. A reminder • Energy cannot be made or destroyed, only transformed (changed). • Energy is measured in Joules. That’s me!

  3. Work In physics, work has a special meaning, different to “normal” English.

  4. Work In physics, work is the amount of energy transformed (changed) when a force moves (in the direction of the force)

  5. Work For example, if Bassem pushes a table, he is doing work against the friction force of the table against the floor.

  6. Calculating work The amount of work done (measured in Joules) is equal to the force used (Newtons) multiplied by the distance the force has moved (metres). Force (N) Distance travelled (m)

  7. Work (J)= Force(N) x distance(m) W = Fscosθ

  8. Important The force has to be in the direction of movement. Carrying the shopping home is not work in physics!

  9. What if the force is at an angle to the distance moved? Work = Fscosθ F θ s

  10. Lifting objects When we lift objects, we are doing work because a force is moving. Force Distance moved

  11. Lifting objects Our lifting force is equal to the weight of the object. Lifting force weight

  12. Let’s look at some examples

  13. Work done (J) = Force (N) x distance (m) A woman pushes a car with a force of 400 N at an angle of 10° to the horizontal for a distance of 15m. How much work has she done?

  14. Work done (J) = Force (N) x distance (m) A woman pushes a car with a force of 400 N at an angle of 10° to the horizontal for a distance of 15m. How much work has she done? W = Fscosθ = 400x15x0.985 W = 5900 J

  15. Work done (J) = Force (N) x distance (m) A man lifts a mass of 120 kg to a height of 2.5m. How much work did he do?

  16. Work done (J) = Force (N) x distance (m) A man lifts a mass of 120 kg to a height of 2.5m. How much work did he do? Force = weight = 1200N Work = F x d = 1200 x 2.5 Work = 3000 J

  17. How much work can you do?

  18. Can you copy this please?

  19. Arm curls Force required = weight of object = mass (kg) x 10 distance

  20. Off you go!

  21. Power!

  22. Power! Power is the amount of energy transformed (changed) per second. It is measured in Watts (1 Watt = 1 J/s) Power = Energy transformed time

  23. Power For each of the people in your table, can you calculate their power?

  24. Work done in stretching a spring

  25. Coursework! • Hooke’s law, spring constant and work

  26. Work done in stretching a spring Work done in strectching spring = area under graph F/N x/m

  27. Revision videos • http://www.youtube.com/watch?v=5EsMmdaYClQ

More Related