A car accelerates at \(5.0 m / s ^{2}\) for \(6 s\), it travels at the speed attained for 20s, and comes to rest after another \(4.0 s\). Calculate the average velocity of the car during the motion
A. \(25.0 m / s\) B. \(20.0 m / s\) C. \(1.25 m / s\) D. \(0.16 m / s\)
Correct Answer: A
Explanation
We sketch the velocity - time graph, We are to calculate the area of this graph. First, you may choose to calculate it using formula for the area of a trapezium \(=1 / 2(a+b) h=1 / 2(20+30) 30\) \(=1 / 2(50) 30=750 m\)ut you must note, this is the total distance and it will be in metres. Total time taken \(=6 s +20 s +4 s =30 s\)verage velocity \(=\frac{750 m }{30 s }\) $$ \Rightarrow 25 ms ^{-1} $$
