# Calculating weight using moments [A-Level] [closed]

A uniform plank of weight 150N and of length 4.0m rests horizontally on two bricks. One of the bricks is at the end of the beam. The other brick is 1.0m from the other end of the plank.

a) Sketch the arrangement and calculate the support force on the plank from each brick

My answer for A was: 50N and 100N.

b) A child stands on the free end of the beam and just causes the other end to lift off its support. Sketch this arrangement and calculate the weight of the child.

I'm stuck on how to solve this question. The answer is supposed to be 150N.

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This isn't homework. I'm finding it difficult to understand the topic, so I'm having a look at the questions. – Deric Oct 9 '11 at 15:47
Hi @Deric and welcome to Phsyics.SE! What causes you to stuck in point b)? Please be more specific on what you understand and what is unclear. – Slaviks Oct 9 '11 at 16:08
I'm not sure how to really begin. Should I take the moment around the brick at the end the plank? – Deric Oct 9 '11 at 16:53
@Deric: we use the "homework" tag here for all problems of an educational nature, and it definitely applies here. Anyway, PSE is not a homework help site, and so we don't take questions of the form "how do I do this problem?" If you can edit the question to ask about the general physics concept that is giving you trouble, then it might be acceptable. See this meta post on homework-style questions for more information. – David Zaslavsky Oct 9 '11 at 18:46

## closed as off topic by Mark Eichenlaub, David Zaslavsky♦Oct 9 '11 at 18:43

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