Question

when brakes are applied to a car moving with a velocity of 54 km^-1 it comes to rest within 2 metre. calculate the frictional resistance if mass of the car is 150 kg

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Answer 1

Explanation:

Initial velocity of the car u = 54 km/h

= 54000/3600 m/s

= 15 m/s

Final velocity v=0

Distance s = 2m

Mass of the car m = 150kg

Acceleration a = ?

Frictional resistance F = ?

We know that

$v {}^{2} = u {}^{2} + 2as$

$= > 0 {}^{2} = 15 {}^{2} + 2a \times 2$

$= > 4a = - 225$

$= > a = - 56.25$

$so \: \: \: a = 56.25ms {}^{ - 2}$

$again$

F = ma

= 150×56.25

= 8437.50 N