A bridge is 50m long, has a mass of 20,000kg, and rests on two pivots, A and B. The distance between A and the left side of the bridge is 10m. The distance between B and the right side of the bridge is 10m.
A lorry drives across the bridge.
i) What is the maximum possible mass of the lorry?
I worked this answer out to be 30,000kg. (10 × M = 20,000 × 15)
But I'm struggling with the second part of the question:
ii) Derive an expression for the force acting upon A and the force acting upon B as a function of x (x = the distance of the lorry from one side of the bridge).
An explanation of how you reached the answer, or some big (:P) hints on how to reach it would be much appreciated.