Question

The speed of a body moving with uniform acceleration is $u$ . This speed is doubled while covering a distance $S$ . When it covers an additional distance $S$ , its speed would become

• A. $\sqrt{3}u$
• B. $\sqrt{5}u$
• C. $\sqrt{11}u$
• D. $\sqrt{7}u$

Answer 1

Answer: (D)

As $v^{2}=u^{2}+2as\Rightarrow \left(2 u\right)^{2}=u^{2}+2as\Rightarrow 2as=3u^{2}$
Now, after covering an additional distance s, if velocity becomes v, then,
$v^{2}=u^{2}+2a\left(2 s\right)=u^{2}+4as=u^{2}+6u^{2}=7u^{2}$
$\therefore v=\sqrt{7}u$