Year 12s: what will be the first way you research your future options? >>

Moments question

How would I answer this momenys question , I am aware the clockwise moment needs to be equal to the anti moment but why do they do 1000 x 2 as part of the answer , I know the formula is distance x force , I would just like some clarification of to why they have done what they have done and then divide by 5 etc...
Thanks

moments.PNG43.7KB

Reply 1

Lauren-x-

Look at the direction of the arrow for weight - you can see that this will turn the anticlockwise, therefore it is an anticlockwise moment, which you can calculate.

Similarly, look at the arrow for the tension - in what direction will this moment act?

You correctly stated the principle of moments, and all the question has done is plug their values into the "sum of anticlockwise moments = sum of clockwise moments" and rearranged for T :smile:

Reply 2

Joinedup

anticlockwise moment
Distance from pivot to centre of mass = 2m
weight = 1000N

moment = 2 x 1000 Nm

---
clockwise moment
distance from pivot to rope attachment = 2+3m
tension = T

moment = 5 x T Nm

----

because the system is in equilibrium the size of the anticlockwise moment is equal to the size of the clockwise moment...

2000 = 5 x T

divide both sides of the equal sign by 5

2000/5=T