(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A mail bag with m = 120 kg is suspended by a vertical rope 8 m long.

1) I have to find the force needed to hold the bag in it's position.

2) I have to find out, how much work is done by the worker in moving the bag to this position.

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3) When a trolley is being pulled up a ramp 4 m, and the ramp inclines 30 degrees, find the work done by the normalforce.

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4) When a rope tied to a body is pulled, the body accelerates. But the body excerts an equal, opposite, force - is the total work done 0?

3. The attempt at a solution

1) I've found F = m*g*tan(a), where a is the angle between the vertical line and the string suspending the bag.

2) I thought of integrating m*g*tan(a) with limits 0 and 30 (degrees, cause 30 degrees is when x = 4 m) and multiplying by 4 m, since W = F*s. Please confirm.

3) I believe it's m*g*cos(30) * 4 m * cos(120) (120 degrees, because of 90 + 0).

4) I believe it is. But it's only an assumption.

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# Homework Help: Various questions, mechanics

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