A force of $$400$$ $$N$$ is applied to the brake drum of $$0.5$$ $$m$$ diameter in a band-brake system as shown in the figure, where the wrapping angle is $${180^ \circ }$$ . If the coefficient of friction between the drum and the band is $$0.25,$$ the braking torque applied, in $$N.m$$ is

A solid circular shaft needs to be designed to transmit a torque of $$50$$ $$N.m.$$ If the allowable shear stress of the material is $$140$$ $$MPa,$$ assuming a factor of safety of $$2,$$ the minimum allowable design diameter in $$mm$$ is

A solid cylinder of diameter $$100$$ $$mm$$ and height $$50$$ $$mm$$ is forged between two frictionless flat dies to a height of $$25$$ $$mm.$$ The percentage change in diameter is

In a single pass rolling process using $$410mm$$ diameter steel rollers, a strip of width $$140mm$$ and thickness $$8mm$$ undergoes $$10\% $$ reduction of thickness. The angle of bite in radians is