Image of an object approaching a convex mirror of radius of curvature 20 m along its optical axis is observed to move from 25/3m to 50/7m in 30 second what is the speed of the object in km/h

Dear Student,
Please find below the solution to your problem.

R = 20 m f =10 m.
From the mirror equation:
1/v1 +1/u1 = 1/f;
1/25/3 + 1/u1 = 1/10;
u1 = - 50 m.
furthermore, when the picture of the question is at 50/7 m.
1/v2+ 1/u2 = 1/f
1/50/7+ 1/u2 = 1/10
u2 = 25m
Contrast out there of the protest = 30-25 = 25m
Speed = relocation/time
= 25/30
= 5/6 m/sec
Speed in km/hr = 5/6 x 18/5
= 3 km/hr

Thanks and Regards