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Work and Power
7th grade Work and Power
| Question | Answer |
|---|---|
| Definition of work | Using a force to move an object through a distance in the direction of the force. |
| What is force? | a push or a pull, also defined as mass x acceleration |
| What force pulls objects down? | gravity |
| What force, from gravity, is a measure of how much an object is pushing down on the ground (or whatever they are on)? | weight |
| formula for work | force x distance |
| unit label for force | N or Newtons |
| unit label for work | J or Joules (equal to N x m/s/s)This is the same as for energy. |
| unit label for energy | J or Joules (same as for work) |
| unit label for power | W or Watts (equal to J/s) |
| SI unit for time | s or seconds |
| SI unit for distance | m or meters |
| formula for power | Energy/time or Work/time |
| What is the purpose of a formula? | to help you know which numbers to use and what to do with them |
| When can there be force and motion, but you cannot calculate the work? | When the motion is not in the direction of the motion. |
| When can energy be used without doing work? | When there is no motion (or none in the direction of the force). |
| If you are trying to find the work and have 10 km as the distance, what is the first step? | Change the distance of 1 km to 10,000 m. |
| If you are trying to calculate power, and the time is 1 hour, what do you need to do first? | Change the 1 hour to 3600 s. |
| Which of these is not needed in calculating work? 10 m, 5 s, 15 N | 5 s, because seconds are a measure of time, and not of force or distance, which are used to calculate work. |