Question

A car accelerates from rest at a constant rate of 2m/s^2 for some time. Then, it retards at a constant rate of 4m/s^2 and comes to rest. IF it remains in motion for 3 seconds, then the maximum speed attained by the car is :

Answer 1

 The time for which the  increases its speed =tSo   v=at=2tor     t=v2−−−−−(1)And    3−t=v4−−−−−(2)Adding eqns (1) and (2) we get        3=v2+v4=3v4or       v=4m/sPutting this value of v in eqn (1) we get            t=42=2sThe distance travelled in 2 second  of its increasing speed is           s1=12×2×2×2=4mThe distance travelled in 1 second  of its decreasing speed is           s2=4×1−12×4×1×1=4−2=2mThe average speed of the car for the journey      vav=total distance covered total time taken=4+23=2m/sThus71. The correct answer is option (2) 2s.72. The correct answer is option (3) 4m/s.73. The correct answer is option (3) 4m.74. The correct answer is option (1) 2m.75. The correct answer is option (1) 2m/s.

Answer 2

The solution is provided in the attachment.
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