Question

A boat is moving with velocity of $3\widehat{i} + 4\widehat{j}$ in river and water is moving with a velocity of $- 3\widehat{i} - 4\widehat{j}$ with respect to ground. Relative velocity of boat with respect to water is :

• A. $- 6\widehat{i} - 8\widehat{j}$
• B. $6\widehat{i} + 8\widehat{j}$
• C. $8\widehat{i}$
• D. $6\widehat{i}$

Answer 1

Answer: (B)

$6\widehat{i} + 8\widehat{j}$

Answer 2

The relative velocity of boat w.r.t. water

$= v_{boat} - v_{water} = (3\mspace{6mu}\widehat{i} + 4\mspace{6mu}\widehat{j}) - ( - 3\mspace{6mu}\widehat{i} - 4\mspace{6mu}\widehat{j}) = 6\mspace{6mu}\widehat{i} + 8\mspace{6mu}\widehat{j}$