Question

A smooth sphere is moving on a horizontal surface with velocity vector $2\hat{i}+2\hat{j}$ immediately before it hits a vertical wall. The wall is parallel to $\hat{j}$ vector and the coefficient of restitution between the sphere and wall is $=\frac{1}{2}$. The velocity vector of the sphere after it hits the wall is

• A. $\hat{i}-\hat{j}$
• B. $-\hat{i}+2\hat{j}$
• C. $-\hat{i}-\hat{j}$
• D. $2\hat{i}-\hat{j}$

Answer 1

Answer: (B)

$-\hat{i}+2\hat{j}$

$v_y=2m/s$
$v_x=-e\times 2=-1m/s$
$\overrightarrow{v}=v_x\hat{i}+v_y\hat{j}=(-\hat{i}+2\hat{j})$ unit