Question

An alpha particle enters a hollow tube of 4 m length with an initial speed of $1\frac{km}{s}$. It is accelerated in the tube and comes out of it with a speed of $9\frac{km}{s}$. The time for which it remains inside the tube is

• A. $8\times {10}^{-3}s$
• B. $80\times {10}^{-3}s$
• C. $800\times {10}^{-3}s$
• D. $8\times {10}^{-4}s$

Answer 1

The correct option is D $8\times {10}^{-4}s$

$v^2=u^2+2as\Rightarrow (9000{)}^2-(1000{)}^2=2\times a\times 4$
$\Rightarrow a=\frac{{10}^{7}m}{s^2}$ Now $t=\frac{v-u}{a}$
$\Rightarrow t=\frac{9000-1000}{{10}^7}=8\times {10}^{-4}sec$