Question

An automobile, travelling at $40$km/h. Can be stopped at a distance of $40$m by applying brakes. If the same automobile is travelling at $120$km/h, the minimum stopping distance in meter, is(assume no skidding)

• A. $270$m
• B. $160$m
• C. $100$m
• D. $360$m

Answer 1

Answer: (B)

$160$m

An automobile, travelling at $=40km/h$

can be stopped at a distance $=40m$

by applying brakes

If the same automobile is travelling at $=120Km/h$

The minimum stopping distance in meter is (assume skidding)

This is called limiting friction.

Magnitude of limiting friction between any two bodies in contact is directly proportional to the normal reaction between them,

$F_1\alpha R$ or $f_1={\mu }_{s}R$

$f_1=$ limiting friction

${\mu }_s=$ co-efficient of friction

$R=$ reaction force

Where in

maximum value of static friction is limiting friction

Direction is always opposite to relative motion

$a=\mu gs=\frac{4^2}{2a}=\frac{4^2}{2\mu g}S\alpha 4^2\frac{S_2}{S_1}=\frac{4^2}{4}=46r{s}_2=160m$