A uniform rod (AB) of mass 80kg and 1.0m lenght is supported on the 2 knife edges placed 15.0cm from its ends. what will be the reactions at these support when a 20kg mass is suspend 10cm from the mid-point of the rod.(workings and diagram)

Answer 1

sum vertical forces. Let fl be the knife edge left support, and fr be the right support.

fl+fr=80+20 in kg

sum moments about the left knife edge.

0=20kg(50-15-10)+80(50-15)-Fr*70

solve for the force right. then in the other equation lf.

Now in newtons, multiply by 9.8, kg is not a force.