Determine the minimum force P that is required to move both

Determine the minimum force P that is required to move both objects.

Determine the minimum force P that is required to move both objects. W 125 N W 245 N 300 mm Surface HS 0.5 0.2

Solution

The friction for rolling and sliding is given as the same

for the first case, whee the force P is acting at 300 mm from the cente of rotation is opposed by the rolling friction force about the axis of rotation.

F = mu x W = mu xm xg

= o.5 x125 x 9.81 + 0.2 x 245 x 9.81 = 1093.815 N

This force creates a torque about the axis of roation and the saame is opposed by the rolling friction torque

Hence P = F = 1093.815 N

In case of sliding, the friction force is given by Mu x N where Mu is the sliding friction coefficiect and N is the Normal force. Normally sliding friction is much more than the rolling friction. In this problem sliding fricion is not given and hence it is assumed the it is same as rolling friction. N is the normal force which is mg.Hence it boils down to the same force of rolling friction calculation.

F = mu1 xN1 + mu2 x N2 = 1093.8 N