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Question
A car is moving with a uniform velocity 30 ms-1. It is stopped in 2 s by applying a force of 1500 N through its brakes. Calculate the following values : The change in momentum of car.
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Solution
Initial velocity, u = 30 m/s
Final velocity, v = 0
Time, t = 2s
Force, F = 1500 N
Here, a = (v - u)/t = (0 - 30)/ 2 = - 15 ms-2. Here, negative sign indicates retardation.
Now, F = ma.
Or, m = F/a = (1500/ 15) = 100 kg.
Change in momentum = Final momentum - Initial momentum
Or, Δp = m (v - u)
Or, Δp = 100 (0 - 30)
Or, Δp = 3000 kg m/s-1
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