A car and driver weighing 7360 N passes a sign stating \"BridgeOut 26.5 m Ahead.

Question

A car and driver weighing 7360 N passes a sign stating "BridgeOut 26.5 m Ahead." She slams on the brakes and the car deceleratesat a constant rate of 9.9 m/s2 . The acceleration due to gravity is 9.8 m/s2 . What is the magnitude of the work done stopping the car if thecar just stops in time to avoid diving into the water? Ans.in units of J. A car and driver weighing 7360 N passes a sign stating "BridgeOut 26.5 m Ahead." She slams on the brakes and the car deceleratesat a constant rate of 9.9 m/s2 . The acceleration due to gravity is 9.8 m/s2 . What is the magnitude of the work done stopping the car if thecar just stops in time to avoid diving into the water? Ans.in units of J.

Explanation / Answer

We must find the initial velocity of the car Let it be u . Final velocity(v) =0 acceleration = -9.9 m/s2 Distance = 26.5 m Using the formula v2-u2=2aS Putting the values 02 - u2 = 2*-9.9*26.5 u = 22.9 m/s Also mass of car and driver = weight / g = 7360 / 9.8 = 751 kg Also as finally kinetic energy is zero . From work energy theorem , Net work done = change in energy Here Change in energy = Final - initial energy                                   = 0 - m*velocity2/2 = -751*22.92/2 = -1.97*105 J Magnitude of work done = 1.97*105 J

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