55.
Which is the correct statement about law of polygon of forces?

56.
The effort required to lift a load W on a screw jack with helix angle $$\alpha $$ and angle of friction $$\varphi $$ is equal to

57.
In actual machines

58.
A heavy ladder resting on floor and against a vertical wall may not be in equilibrium, if

59.
The C.G. of a right circular solid cone of height h lies at the following distance from the base

60.
According to principle of moments