Question

There is a uniform electric field of strength ${10}^3$ V/m along y-axis. A body of mass 1g and charge ${10}^{-6}$C is projected into the field from origin along the positive x-axis with a velocity 10m/s. Its speed in m/s after 10s is (Neglect gravitation)

• A. 10
• B. $5\sqrt{2}$
• C. $10\sqrt{2}$
• D. 20

Answer 1

The correct option is C $10\sqrt{2}$

Body moves along the parabolic path.


For vertical motion : By using $v=u+at$

$\Rightarrow v_y=0+\frac{QE}{m}.t=\frac{{10}^{-6}\times {10}^3}{{10}^{-3}}\times 10=10m/sec$

For horizontal motion - it;s horizontal velocity remains the same i.e after the same i.e after 10 sec, horizontal
velocity of body $v_x=10m/sec.$
Velocity aftey 10 sec $v=\sqrt{V_x^2+V_y^2}=10\sqrt{2}m/sec$