NTA Abhyas JEE Main2020PhysicsMotion in Two DimensionsPractice
A large flat metal surface has a uniform charge density + σ . An electron of mass m and charge ρ leaves the surface at the point A with speed u and returns to it at point B . Disregarding gravity the maximum value of AB is
Options
- A4u 2 m ε 0 σ ρ
- Bu 2 ⋅ ρ ε 0 m σ
- C2 ε 0 m u 2 ρ σ
- Du 2 σ ρ ε ⋅ m
Correct answer
C. 2 ε 0 m u 2 ρ σ
Step-by-step solution
Electric field due to one surface of the large metal plate, The projected electron's motion will be on a curved path like a projectile. ∴ AB will be maximum when θ = 45 ° Range A B m a x = u 2 a a = ρ E m = ρ σ 2 ε 0 m = u 2 ρ σ 2 ε 0 m = 2 ε 0 m u 2 ρ σ