- What is a moment of a force
- How do you calculate the moment of a force
- What are the units of moments
- What is the principle of moments in plain language
- How would I write this in an exam
- How many marks will I get.
- How do I do exam questions
- Is there anything else
- What about difficult moment questions
It's a number which describes the turning effect of force. For your exam, the turning can be clockwise of anticlockwise
Multiply the value of the force by the perpendicular distance from the turning point (pivot)
Newton metres (Nm)
When you add up all the moments acting on an object in equilibrium, the result is zero. There are two flavours of moments, clockwise and anticlockwise ones. The sum of all the anti clockwise moments will be equal to the sum of all the clockwise moments. It doesn't matter where you choose your pivot(point)the two different types of moments will be equal
In equilibrium, the sum of the clockwise moments= the sum of the anti clockwise moments about any point.
You'll get one mark for saying "In equilibrium" and another mark for the rest of it. Lots of people forget this point and so lose one mark
If you recognise the question as moments write down:
(i) the sum of the clockwise moments= the sum of
the anti-clockwise moments
(ii) Figure out which point to use as the
pivot (usually a place where an unknown force acts)
(iii) Plug in the
figures
(iv) Solve the equation.
Yes. If an object is in equilibrium the total forces acting in one direction = the total forces acting in the opposite direction . This fact often helps you to work out another unknown force or distance
These usually happens when you have to use sin, cos or tan to work out the perpendicular distance from the point. Once you have done this, the rest is straight forward.