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Isaac Physics moments question

There are two questions I'm really stuck on TT_TT can someone help me out pleasee??
1) A metre stick has its centre of mass at the 50cm mark, and weighs 0.92N . A 2.00N weight is stuck to the 10cm mark with massless glue. About which point will the ruler balance?
I got 77 cm as an anwer (to 2 sf) as i assumed the total moments anticlockwise would be 2.92, and so the moments clockwise would have to equal that. Then taking the centre of mass as pivot i said that 2Nx40cm=2.92xdistance TT_TT got 27.4 by rearranging and then added it to 50 cm. Well, that's wrong and i don't undertand whyyyy.
Next question
2) A 200 m bridge span is supported at both ends. The span weighs 100 tonnes . A 30 tonne bus is 50m from one end of the span. Calculate the supporting force holding the bridge up at the end nearer the bus. Please give your answer to 2 significant figures.
Help please :smile:
What level are these questions?
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Azzy_wazzy
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Original post by WhiteScythe
What level are these questions?

You mean on Isaac Physics?? It doesn't say for some reason, our teacher assigned us the moments board, they're from there
Original post by Azzy_wazzy
There are two questions I'm really stuck on TT_TT can someone help me out pleasee??
1) A metre stick has its centre of mass at the 50cm mark, and weighs 0.92N . A 2.00N weight is stuck to the 10cm mark with massless glue. About which point will the ruler balance?
I got 77 cm as an anwer (to 2 sf) as i assumed the total moments anticlockwise would be 2.92, and so the moments clockwise would have to equal that. Then taking the centre of mass as pivot i said that 2Nx40cm=2.92xdistance TT_TT got 27.4 by rearranging and then added it to 50 cm. Well, that's wrong and i don't undertand whyyyy.
Next question


should have subtracted from 50... the balance point is going to move towards the 2.00 mass i.e. away from 50cm and towards 10cm - probably drawing a diagram would help.

2) A 200 m bridge span is supported at both ends. The span weighs 100 tonnes . A 30 tonne bus is 50m from one end of the span. Calculate the supporting force holding the bridge up at the end nearer the bus. Please give your answer to 2 significant figures.
Help please :smile:


taken moments about the end furthest away from the bus?

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