A balloon is rising up along the axis of a concave mirror of radius of curvature `20 m` A ball is dropped from the balloon at a height `15m` from the mirror when the balloon has velocity `20m//s` .Find the speed of the image of the ball formed by concave mirror after `4` seconds[take:`g=10m//s^(2)`]

Answer

80m/s

Explanation

Speed of ballon = 20 m/s

d= `20 xx 4 xx (1)/(2) xx 10 xx 16`
d=0
`u=-15 , R=-20 , f=-10`
`v= (ub)/(u-f) = (150)/(-5) = -30`
`m= -(v)/(u) = (30)/(-15) = -2 , v_(0) = -20`
`v_(1)=-m^(2)v_(0)= -4 xx -20 = 80`