An electric train accelerates uniformly from rest to a speed of 20m/s which it maintains until the brakes are applied. It is then brought to rest by a uniform retardation equal in magnitude to twice its former acceleration. The total distance covered is 7.8 km and time taken is is 7 minutes.


  • the time for which the train is travelling at constant speed,
  • the initial acceleration in m/s^2.

closed as too localized by Waffle's Crazy Peanut, Manishearth Mar 22 '13 at 12:56

This question is unlikely to help any future visitors; it is only relevant to a small geographic area, a specific moment in time, or an extraordinarily narrow situation that is not generally applicable to the worldwide audience of the internet. For help making this question more broadly applicable, visit the help center. If this question can be reworded to fit the rules in the help center, please edit the question.

  • $\begingroup$ Hi Taiyaba. Welcome to Physics.SE. This site deals with conceptual Physics Q&A. We don't encourage homework questions that doesn't involve any sort of work done by the author (which is you) and asks other users to solve the problem. If you think you could clarify your question, add what you've done along with your question. We're ready to help you. If you aren't clear, Please have a look at our homework policy for more info. After improving the post, flag it for moderator attention. $\endgroup$ – Waffle's Crazy Peanut Mar 22 '13 at 12:53

Get a graphical approach to this kind of question.enter image description here

see this V-T graph of the scenario.

You can find everything. the slope gives acceleration.


Not the answer you're looking for? Browse other questions tagged or ask your own question.