posted by Usman .
A uniform rod of mass 100g has a length of 1m.it is supported horizantally on two knife edges placed 10cm from it end. What will be the reaction at these supports when a 50g mass is suspended 30cm from one of the knife edges?
from one knife edge
center of rod is .4 meters
added mass is .3 meters
other knife edge is .8 m away from first
total mass = .1 + .05 = .15 kg
moment around close knife edge = g(.3*.05+.4*.1) = .055 g
F(.8) = .055 g
F = .06875 g
if g = 9.81 m/s^2
F = .674 Newtons
total weight = .15(9.81) = 1.47 N
so other F = 1.47 - .674 = .798 Newtons