Question

Question: A 4m, 500kg steel beam extends horizontally from thepoint where it has been bolted to the framework of a new buildingunder construction. a 70kg worker stand at the far end of the beam.What is the magnitude of the torque about the point where the beamis bolted into place.

Now this is what I have:

τ (grav)=-MgXcm where Mg is the net gravitational forceacting on the object and Xcm is the moment arm between the rotationaxis and center of mass.

=2.13 from the rotation point (where the building is bolted)

Now the problem I think I am having is finding the net forceon the object. I thought it was the total mass of the object(570kg) times gravity (9.8)

This give the final answer to be

-(570)(9.8)(2.13)=-11898.18Nm but that is not the answer. Theanswer is -12500Nm.

Any help would be appreciated. Thanks

Answer 1