A disc of radius 2 m and mass 100 kg rolls on a horizontal floor . Its centre of mass has speed of 20 cm/s . How much work is needed to stop it ?

A disc of radius 2 m and mass 100 kg rolls on a horizontal floor . Its

1.	A disc of radius 2 m and mass 100 kg rolls on a horizontal floor . Its centre of mass has speed of 20 cm/s . How much work is needed to stop it ?
Answer» 1 J 3 J 30 kJ 2 J Solution :Required work DONE = `- (K_(f) - K_(i)) = 0 + K_(i) = K_(i)` `= (1)/(2) I omega^(2) + (1)/(2) mv^(2) = (1)/(2) ((1)/(2) mR^(2)) omega^(2) + (1)/(2) mv^(2)` `= (3)/(4) mv^(2) = (3)/(4) xx 100 xx (20 xx 10^(-2))^(2) = 3J`