This question is so easy I'm embarrassed to ask but i don't know the answer :)
A uniform metre rule of mass 100g balances at the 40cm mark when a mass X is placed at the 10cm mark. What is the value of X
I presume this means the pivot is at 40 cm and the mass is placed at the 10cm mark so its perpendicular distance from pivot is 30cm
but i don't know how to take into account the pivot isn't in the middle and hence the weight of the metre rule on either side.