A car , moving with a speed of `50 km//hr` , can be stopped by brakes after at least ` 6m `. If the same car is moving at a speed of `100 km//hr`, the minimum stopping distance is

Options

A. 12 m
B. 18 m
C. 24 m
D. 6 m

Answer

C

Explanation

Initial extension will be equal to 6m.
Initial energy `= (1)/(2)(200)(6)^(2) = 3600 J`
Reaching As we get `(1)/(2) mv^(2) = 3600 J`
`mv^(2) = 7200 J`
From FBD at A, we get `N = (mv^(2))/(R ) =(7200)/(5) = 1440 N`