A) It is one-fourth of the weight of the car.
B) It is two-thirds of the weight of the car.
C) It is one-eighth of the weight of the car.
D) It is four-fifths of the weight of the car.
Correct Answer: A
Solution :
\[{{0}^{2}}-{{7}^{2}}=2a\times 10=2.45\,\,m\,\,{{s}^{-2}}\] Let \[m\] be the mass of the motor car. Therefore, resistance due to brakes, \[F=ma=m\times 2.45\,\,N\],\[\therefore \]\[\frac{F}{mg}=\frac{m\times 2.45}{m\times 9.8}=\frac{1}{4}\]
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