Question

The velocity of an object at $t=0$ is $\overrightarrow{v_0}=-4\hat{j}m/s$. It moves with constant acceleration $\overrightarrow{a}=(3\hat{i}+8\hat{j})m/s^2$. What is its velocity at $t=1s$?

• A. $(3\hat{i}+8\hat{j})m/s$
• B. $(3\hat{i}-6\hat{j})m/s$
• C. $(3\hat{i}+4\hat{j})m/s$
• D. $(7\hat{i}+4\hat{j})m/s$

Answer 1

Answer: (C)

$(3\hat{i}+4\hat{j})m/s$

Given,

$\overrightarrow{u}=v_0=-4\hat{j}m/s$

$\overrightarrow{a}=(3\hat{i}+8\hat{j})m/s^2$

$t=1sec$

From 1st equation of motion,

$\overrightarrow{v}=\overrightarrow{u}+\overrightarrow{a}t$

$\overrightarrow{v}=-4\hat{j}+(3\hat{i}+8\hat{j})\times 1$

$\overrightarrow{v}=-4\hat{j}+3\hat{i}+8\hat{j}$

$\overrightarrow{v}=(3\hat{i}+4\hat{j})m/s$

The correct option is C.