A 1 kg block is resting on a surface with coefficient of friction $$\mu $$ $$=0.1.$$ A force of $$0.8$$ $$N$$ is applied to the block as shown in the figure. The friction force is

The coefficient of restitution of a perfectly plastic impact is

A streamline and an equipotential line in a flow field

Figure shows the schematic for the measurement of velocity of air (density $$ = 1.2\,\,kg/{m^3}$$ ) through a constant -area duct using a Pilot tube and a water-tube manometer. The differential head of water (density $$ = 1000\,kg/{m^3}$$) in the two columns of the manometer is $$10$$ $$mm.$$ Take acceleration due to gravity as $$9.8$$ $$m/{s^2}.$$ The velocity of air in $$m/s$$