In a region an electric field is setu!l with its strength `E = 15 N//C` and it makes an angle of `30°` with the horizontal plane as shown in figure. A ball having a charge 2C, mass 3kg and coefficient of restitution with ground 0.5 is projected at an angle of `30°` with the horizontal along the direction of electric field with speed 20 m/s. Find the horizontal distance travelled by ball from first hit with the ground to the second time when it hits the ground.

Answer

C

Explanation

`qE=3N,` vertical of electric force `=30sin30^@=15N` and horizontal component of eledtric force `=30 cos 30^@=15sqrt3=15sqrt3N`
`a_y+(2u_y)/a_y=(2xx20sin30^@)/5=4s`
`T_2=eT_1=2s`
Horizontal velocity after first drop
`=(20cos30^@)+a_xT_1`
`=(10sqrt3)+(5sqrt3)4`
`=30sqrt3m//s`
`:.` Horizontal distance travelled between first drop and second drop
`=(30sqrt3)RT_2+1/2a_xT_2^2`
`=(30sqrt3)(2)+1/2(5sqrt3)(2)^2`
`=70sqrt3m`