script

 In plain terms, acceleration is the rate of increase of velocity. The symbol for acceleration is a. To calculate acceleration of an object, we use the following equation: a = Dv / Dt In this equation a = acceleration, Dv = change in velocity, and Dt = change in time. If the acceleration of the object is the same for all time intervals, the acceleration then is said to be constant or uniform. Acceleration is measured in meters per second per second or m/s/s, or m/s2. Other equations that are related to acceleration are: Velocity of an object with constant acceleration: vf = vi + at In the above equation vf = final velocity of the object, vi = initial velocity of the object, a = acceleration, and t = time. Displacement during constant acceleration: d = 1/2(vf + vi)t The variables in the above equation are the same as in the previous equation. Displacement when acceleration and time are known: d = vit + 1/2at2 The above equation is composed of two terms. The first term, vit, corresponds to the displacement of an object if it were moving with constant velocity, vi. The second term, 1/2at2, gives the displacement of an object starting from rest and moving with uniform acceleration. The sum of these two terms gives displacement of an object that starts with an initial velocity and accelerates constantly. Displacement when velocity and acceleration are known: vf2 = vi2 + 2ad Acceleration due to gravity. This type of acceleration is given a special symbol, g. Since acceleration is a vector quantity, it has magnitude (size) and direction. On the surface of the Earth, the freely falling object has the following acceleration: g = -9.80 m/s2. Assuming there is no air resistance, all equations given in this section can be modified to apply to falling object, by simply replacing a with g.

 August 1999 © 1999, Physics by Demonstrations