Question

A uniform meter rod is balanced at 40 cm mark when a load of 20N is suspended at 10 cm mark. the weight of meter rod is:

A) 20 N
B) 25 N
C) 60 N
D) 40 N​

Answer 1

Answer:

D) 40 N

Explanation:

You can simplify the problem by assuming the weight of the rod is concentrated at the centre of mass, at the 50 cm mark; this simplification is good for a non-accelerating system. It’s more complicated if the rod’s pivoting under the load.

So you have a 40 newton load 20 cm one side of the pivot, balancing the weight of the rod the same distance, 20 cm, the other side. That makes the weight of the rod 40 newtons, I think. For full marks, (1) spell “newtons” with a small “n”, as that’s the convention for units (although, confusingly, the abbreviation is “N”); (2) hope your teacher doesn’t use Quora and spots your question here. You forgot to ask it anonymously, Elixabeth Lichu and Ijaz Khan.

So the answer’s 40 newtons or 40 N.