Question

Question 22(i)
An electron moving with a velocity of $5\times {10}^{4}m{s}^{-1}$ enters into a uniform electric field and acquires a uniform acceleration of ${10}^{4}m{s}^{-2}$ in the direction of its initial motion.

(i) Calculate the time in which the electron would acquire a velocity double of its initial velocity.

Answer 1

Given initial velocity, $u=5\times {10}^{4}m{s}^{-1}$ and acceleration, $a={10}^{4}m{s}^{-2}$
(i) Final velocity $=v=2u=2\times 5\times {10}^{4}m{s}^{-1}=10\times {10}^{4}m{s}^{-1}$
To find t. use v=u+at
Or $t=\frac{v-u}{a}$
$\left(\frac{10\times {10}^4-5\times {10}^4}{{10}^4}\right)=\frac{5\times {10}^4}{{10}^4}=5s$