Question #5c358

1 Answer
Apr 17, 2016

The weight of S is 16N

Explanation:

You need to consider moments about the fulcrum (the knife edge). Looking at the weights on the right hand side (clockwise moments).
The moments are:

  • 10N×0.2m -the weight acting at the centre of the rod which is 20cm from the fulcrum; and
  • 8N×0.35m -the 8N weight that is 35cm from the fulcrum.

So total = 2Nm+2.8Nm=4.8Nm

For the system to be in equilibrium, this must equal the anticlockwise moments due to the unknown solid =S×0.3m

Hence

0.3S=4.8
so S=4.8/0.3=16N