Question

A body is moving under the action of two forces${\overrightarrow{F}}_{1} = 2\widehat{i} - 5\widehat{j};{\overrightarrow{F}}_{2} = 3\widehat{i} - 4\widehat{j}$. Its velocity will become uniform under a third force ${\overrightarrow{F}}_{3}$given by :

• A. $5\widehat{i} - \widehat{j}$
• B. $- 5\widehat{i} - \widehat{j}$
• C. $5\widehat{i} + \widehat{j}$
• D. $- 5\widehat{i} + \widehat{j}$

Answer 1

Answer: (D)

$- 5\widehat{i} + \widehat{j}$

Answer 2

For uniform velocity, acceleration is zero. Hence resultant force will be zero

$\therefore\overset{\rightarrow}{F_{1}} + {\overset{\rightarrow}{F}}_{2} + \overset{\rightarrow}{F_{3}} = 0$

}{or\overset{\rightarrow}{F_{3}} = ( - 5\overset{\land}{i} + 9\overset{\land}{j})}$$