Question

An electron moving with a velocity of 5 × 10⁴ m s^-1 enters into a uniform electric field and acquires a uniform acceleration of 10⁴ 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. 

(ii) How much distance the electron would cover in this time?

Answer 1

Given initial velocity, u = 5 × 10⁴ m s^-1 

and acceleration, a = 10⁴ m s^–2 

(i) final velocity = v = 2 u = 2 × 5 ×10⁴ m s^–1 =10 × 10⁴ m s^–1 

To find t,      use  v  =  at 

                    or t = u - u / a

(ii)           Using s = ut + 1/ 2 at ² 

= (5 ×10⁴) × 5 + 1/ 2 (10 ) × (5) ² = 25 ×10⁴ + 25 /2 ×10⁴ = 37.5×10⁴ m