photo credit: lululemonathletica

A marathon runner is running at a speed of 2.1 m/s and decides it’s time to pick up the pace.  For the next 17 m she accelerates at a rate to 0.15 m/s2.  What is her speed when she is done?

average acceleration physics problem with answer

What to watch for when solving a problem like this:

  • Whenever you use the V2 = Vo2 +2ax formula you need to be really careful that you don’t forget the exponents!  This is a very common mistake that is made when using this particular formula.  I recommend making sure you’ve done everything right by “checking the units” like shown on the right side of this problem in the “extra” column.
  • Watch your order of operations when doing the math for this problem … that is, make sure you don’t rush through the math and that you do things in the proper order: Brackets, Exponents, Division, Multiplication, Addition, Subtraction.
  • One mean trick that can be played on you with this type of question is sometimes the way they phrase the question can be really misleading.  For example this one says “What is her speed when she is done?” …. done what?!? … the race, the acceleration, the day?  Don’t let your imagination get to crazy on you … the general rule is to keep it simple and solve for the most obvious thing :)