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  • Help me please, An automobile, travelling at 40 km/h, canbe stopped at a distance of 40 m byapplying brakes. If the same automobileis travelling at 80 km/h, the minimumstopping distance, in metres, is (assume noskidding) :

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 80 km/h, the minimum
stopping distance, in metres, is (assume no
skidding) :

  • Option 1)

    75 m

  • Option 2)

    100 m

  • Option 3)

    150 m

  • Option 4)

    160 m

 

Answers (2)

best_answer

As we learned 

 

Limiting Friction -

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

F_{l}\;\alpha\ R  or   f_{l}=\mu_{s}R

f_{l}= limiting friction 

\mu_{s}= coefficient of friction

R = reaction force

- wherein

*    Maximum value of static friction is limiting friction.

*     Direction is always opposite to relative motion.

 

 a = \mu g

s= \frac{4^{2}}{2a} = \frac{4^{2}}{2\mu g}

s\alpha 4^{2}

\frac{s_{2}}{s1_{1}} = \left ( \frac{4_{2}}{4_{1}} \right ) = 4 or s_{2}= 160m


Option 1)

75 m

Option 2)

100 m

Option 3)

150 m

Option 4)

160 m

Posted by

Plabita

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