Practicing Success
A solid sphere is given a horizontal velocity of 4m/s on a flat surface. What will be its velocity when it starts pure rolling? Mass = 2kg, Radius = 5cm. Coefficient of friction = 0.3. |
3s 2s 2/3 s It cannot roll purely |
2/3 s |
Friction force ‘f’ will cause its speed to come down & increase its angular speed till V = Rw. f = μN = 0.3*2*10 = 6N. Thus, deceleration ‘a’ = 6/2 = 3 m/s2. And, angular acceleration = a/R = 3/0.05 = 60 rad/s2. v = vo – at = 4 – 3t. w = wo + (a/R)t = 0 + 60t = 60t. At pure rolling, v = Rw ⇒ 4 – 3t = 0.05(60t) ∴ 4 = 3t + 3t = 6t. ∴ t = 2/3 s. |