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# Help! watch

1. Could someone help me through this worksheet please

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2. This took me far too long.

Right, so the system is in equilibrium because nothing moving. The forces up equal for the forces down. What this means is the moments in the system are also in equilibrium. We've got a cantilever beam (a beam with one end fixed) and loads across it, that - without a reaction, would cause the beam to swing down. So, there is a reaction momentum at C that counter acts this gravitational moment.

This means there is a reaction force UP at C we'll call it R multiplied by the Length L of the beam to counteract the moments DOWN across the length of the beam. This means we can form the equation...

RL = (10g x 3) + (5g x 1.5). Where g is gravitational acceleration. We're working with moments not forces so we multiply by the distance as taken from point C.
You may prefer... RL - (10g x 3) - (5g x 1.5) = 0; i.e. net moments equal 0.

So... from that we can calculate the reaction force R = 122.6 N

Then, it's just trigonometric. You have a force up from C of 122.6N and a known angle of 30 degrees. You should be able to calculate from that, that the Tension force along is about 245.2N

If you need more help, no trouble, the rest should be apparent if your maths is up to scratch. Best of luck!

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Updated: October 13, 2013
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