A car, moving with a speed of `50 km//hr`, can be stopped by brakes after at least `6 m`. If the same car is moving at a speed of `100 km//hr`, the minimum stopping distance isA. 6 mB. 2 mC. 18 mD. 24 m

A car, moving with a speed of `50 km//hr`, can be stopped by brakes af

1.	A car, moving with a speed of `50 km//hr`, can be stopped by brakes after at least `6 m`. If the same car is moving at a speed of `100 km//hr`, the minimum stopping distance isA. 6 mB. 2 mC. 18 mD. 24 m
Answer» Correct Answer - D Using work - energy theorem `W_("total") = Delta K` i.e.., work done by stopping forces should be equal to change in the kinetic energy of car. `-F_("stopping") xx "stopping distance" = (k_("final") - k_("initial"))` `rArr -F_("stopping") xx s=(0 -(1)/(2)mv_("initial")^(2))` `rArr F_("stopping") xx s = (1)/(2) mv_("inital")^(2)` As stopping force is same for both the cars, hence `s prop v_("initial")^(2)` `rArr (s_(1))/(s_(2)) = ((v_("initial")^(2))_(1))/((v_("Initial")^(2))_(2))` or `(6)/(s_(2))=((v_("initial")^(2))_(1))/((v_("initial")^(2))_(2)) = ((50)/(100))^(2) rArr s_(2) = 24 m`.

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A car, moving with a speed of `50 km//hr`, can be stopped by brakes after at least `6 m`. If the same car is moving at a speed of `100 km//hr`, the minimum stopping distance isA. 6 mB. 2 mC. 18 mD. 24 m

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