Thank-you for answering my question A car is travelling at 18 in s-1 when the dr

Question

Thank-you for answering my question

A car is travelling at 18 in s-1 when the driver brakes suddenly. The wheels lock and the car skids in a straight line to a stop. The coefficient of friction between the tyres and the road is 0.4. How far docs the car travel from the point at which the brakes arc applied until it conics to a halt? Two objects A and B of respective masses mA = 8.00 kg and mB = 2.00kg are travelling towards each other along the x-axis with velocities uAx = 10.0 in s-1 and mBx = -5.00 ms-1 when they collide and coalesce into a single object. After the collision, the combined object moves along the x-axis. How much energy is lost in the collision?

Explanation / Answer

The speed of the car before breaks applied is u = 18 m/s The coefficient of friction is = 0.4 Let the car travelled a distance of d the initial kinetic energy of the car is Ki = 0.5mu2 The final kinetic energy of the car is Kf = 0        (stopped) the change in kinetic energy K = 0.5mu2 According to the work energy theorem, this change in kinetic energy will result in the work donr byb thr frictional force on the car The waork done by the frictional force is W = mgd g is the acceleration due to gravity Therfore mgd = 0.5mu2 d = u2/g    = (18 m/s)2/(0.4)(9.8 m/s2)    = 82.65 m d = u2/g    = (18 m/s)2/(0.4)(9.8 m/s2)    = 82.65 m

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