- #1

I-need-help

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## Homework Statement

Consider a mechanical car jack. To change a wheel it may need to lift a load of 2000N. Suppose that one rotation of the screw raises the car by 10mm. You apply a force to the end of the lever, 0.5m long, through a full circle. The jack is only 40% efficient. Calculate the force that you have to apply.

(This is a textbook question from OCR, AS Physics.)

## Homework Equations

probably to do with moments:

**anti-clockwise moments = clockwise moments**

work done:

**work done = force x perpendicular distance...**

GPE:

**gravitational pe = mass x g x height**

I don't know where to begin, etc..

## The Attempt at a Solution

There is answer at the back of the textbook, but I won't show it for now, so that it doesn't affect your way of workings, or anything... I'll show it if needed though.

Thank you for any help!