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QUESTION:
A car of mass 480 kg moving at a speed of 54 kmph, is stopped by applying brakes in 10 s. Calculate the force applied by the brakes.
ANSWER:
The force applied by the brakes = 720 N.
GIVEN:
A car of mass 480 kg moving at a speed of 54 kmph, is stopped by applying brakes in 10 s.
TO FIND:
The force applied by the brakes.
EXPLANATION:
★ v = u + at
=> u = 54 kmph = (54 × 5) ÷ 18 = 15 m/s
=> v = 0
=> t = 10 s
=> 0 = 15 + 10a
=> 10a = - 15
=> a = - 1.5 m/s²
★ Force = ma
=> m = 480 kg
=> a = - 1.5 m/s²
=> F = - 480 × 1.5
=> F = - 720 N. [Negative sign indicates force is applied in opposite direction to the motion of the car ]
Hence the force applied by the brakes = 720 N.
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