The adjacent diagram shows a heavy roller, with its axle at O, which is to be raised on a pavement XY. If there is friction between the roller and pavement, show by an arrow on the diagram the point of application and the direction of force to be applied. If pivoted at 0, now will it go up?

Define the moment of a couple. Write its S.I unit.

State the condition when a body is in

(i) static equilibrium.

(ii) dynamic equilibrium.

Give one example each of static and dynamic equilibrium.

State two conditions for a body, acted upon by several forces to be in equilibrium.