Image of an object approaching a convex mirror of radius of curvature 20 m along its optical axis is observed to move from (25/3)m to (50/7)m in 30 s . If the object is moving uniformly, then its speed is

Question

Image of an object approaching a convex mirror of radius of curvature 20 m along its optical axis is observed to move from (25/3)m to (50/7)m in 30 s . If the object is moving uniformly, then its speed is (A)  3 km h- 1 (B)  4 km h- 1 (C)  5 km h- 1 (D)  6 km h- 1

Tardigrade Admin · Accepted Answer

Using mirror formula, Or (1/u1)= (3/25) - (1/10) Or u1 = 50 m And ∴ (1/u2) = (7/50) - (1/10) Or u2 = 25 m Speed of object =(u1 - u2/t i m e) =(25/30 )m s- 1 = 3 km h- 1

Q. Image of an object approaching a convex mirror of radius of curvature $20 m$ along its optical axis is observed to move from $\frac{25}{3} m$ to $\frac{50}{7} m$ in $30 s$ . If the object is moving uniformly, then its speed is

$3 km h^{- 1}$

$4 km h^{- 1}$

$5 km h^{- 1}$

$6 km h^{- 1}$

Using mirror formula,
Or $\frac{1}{u _{1}} = \frac{3}{25} - \frac{1}{10}$
Or $u_{1} = 50 m$
And
$∴ \frac{1}{u _{2}} = \frac{7}{50} - \frac{1}{10}$
Or $u_{2} = 25 m$
Speed of object $= \frac{u _{1} - u _{2}}{t im e}$
$= \frac{25}{30} m s^{- 1}$
$= 3 km h^{- 1}$

Q. Image of an object approaching a convex mirror of radius of curvature 20m along its optical axis is observed to move from 325​m to 750​m in 30s . If the object is moving uniformly, then its speed is

3kmh−1

4kmh−1

5kmh−1

6kmh−1