Question

A particle has initial velocity $(3\hat{i}+4\hat{j})$and has acceleration $(0.4\hat{i}+0.3\hat{j})$. Its speed after $10\text{s}$ is

• A. $7\sqrt{2}\text{units}$
• B. $7\text{units}$
• C. $10\text{units}$
• D. $8.5\text{units}$

Answer 1

The correct option is A $7\sqrt{2}\text{units}$

From first law of motion
$\overrightarrow{v}=\overrightarrow{u}+\overrightarrow{a}t=(3\hat{i}+4\hat{j})+(0.4\hat{i}+0.3\hat{j})10=7\hat{i}+7\hat{j}$
$\therefore |\overrightarrow{v}|=\sqrt{7^2+7^2}=7\sqrt{2}\text{units}$