Acceleration Problems!  Yee Haw!

Basic Formula: A = Vf-Vi / t A = Acceleration
Vf = Final Velocity Vi = Initial Velocity t = time
Units: Velocity will always be a distance unit over a time unit.  (mi/hr) (m/sec) (km/hr)
Acceleration will always be a velocity (m/s, mi/hr) over a time (sec).  Examples would be:  m/s/s or m/s2
Time units: min (minute), sec (second), hr (hours)


These problems are not really very hard to solve as long as you match the given numbers (usually using their units) with the formula above.  You can also use the triangle method.  The triangle is an easy way to figure out how to manipulate the formula.  In order to use it, look at the triangle.  Put your finger over the variable or letter you need to solve for.  For example, if you are looking for the acceleration, you will cover up the letter A.  Now you do the mathematical function it shows.  If the letters are beside each other, you multiply.  This formula is bit more complicated just because it has the Vf and Vi. These are not all that bad.  The Vf is the final velocity of the object.  The Vi is the starting velocity.  We have to know both since acceleration is a average change.  If one is on top of the other, you divide.  If you would like to check out some sample problems, click on this link:  <acceleration sample problems>
The triangle:

You can see that if you were trying to solve for acceleration.  Then the (Vf-Vi) would be over the T, so you would divide the change in velocity that happened by the time it took.  Similarly, if you wanted to solve for the time it took, then the change in velocity would be divided by the acceleration since the change in velocity is on the top. If you wanted to solve for change in velocity, then the acceleration would be located beside the time, so you would multiply them together.  NOTE:  If your object is slowing down, the the Vf - the Vi will give you a negative number.  When you divide that by the positive time, you will get a negative number.  THAT IS CORRECT!  Slowing down gives a negative acceleration.  Speeding up gives a positive one. :)



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