Multiple choice

The front end and the back end of a train moving on a straight track with uniform acceleration pass an electric post with speeds $\sqrt {11} km/h$ and $\sqrt {21} km/h$ respectively. What is the speed with which the middle point of the train passes the same electric post?

  1. $3.5\ km/h$
  2. $\dfrac {\sqrt {11} + \sqrt {21}}{2}\ km/h$
  3. $4\ km/h$
  4. $4.75\ km/h$
Reveal answer Fill a bubble to check yourself
B Correct answer