Question

A wheel starting from rest, rotates with a uniform angular acceleration of $2{\text{rad/s}}^2$. The number of rotation it performs in the tenth second is

• A. 3
• B. 6
• C. 9
• D. 12

Answer 1

The correct option is A 3

$\begin{array}{cc}{S}_n& =u+\frac{1}{2}a(2n-1)[Givenn=10]\\ {\theta }_n& ={\omega }_i+\frac{1}{2}\alpha (2n-1)\\ {\theta }_n& =0+\frac{1}{2}\times 2(2\times 10-1)\\ & =19\\ {\theta }_n& =19\text{rad}\end{array}$

Rotations = $\frac{19}{2\pi }$ =$\frac{19}{2\left(3.14\right)}$ = 3 (apprx.)