# Upward force on beam

A 3.0-m-long rigid beam with a mass of 100 kg is supported at each end. A
80 kg student stands 2.0 m from support 1. How much upward force does support 1 exert on the beam?

I first found the weight of the student to be 784N.
so 784N*2cm =F*3cm
F= 522.67N
is this right?

No, its not. I think you forgot to take the moment caused by the weight of the beam.
I think this is how it should be done:
(2x784)+(1.5x980) = 3xF
This gives us the value of F(Force on the other support)=1012.67N
Substracting this value from the total downward force(784N+980N) we get the upward force exerted by the support1 be 751.33N

DeathKnight said:
No, its not. I think you forgot to take the moment caused by the weight of the beam.
I think this is how it should be done:
(2x784)+(1.5x980) = 3xF
This gives us the value of F(Force on the other support)=1012.67N
Substracting this value from the total downward force(784N+980N) we get the upward force exerted by the support1 be 751.33N

Yes, I forgot to consider the weight of the beam.
Thanks.