Kinematics: Motion in One Dimension

Free Fall

Falling rock sign

What happens when you increase the angle of the incline so much that it is vertical? That’s right! The object falls. So, when you look at objects that fall, you treat them as objects undergoing a constant acceleration—the acceleration of gravity, 9.80 m/s2. Acceleration of gravity is a vector quantity so we need to be careful how we label it. If you determine that the +y is upward, then the acceleration of gravity will be negative; if +y is downward, the acceleration is positive. Just use your common sense when doing calculations—make sure to consider the direction when plugging in values of velocity and acceleration into any problems associated with motion.

Key concept Mathematical Models: Free Fall

v sub y equals v nought sub y plus g times t; y equals y nought plus v nought sub y times t plus one half g times t squared; v sub y squared equals v nought y squared plus 2 g times the quantity y minus y nought

Notice here the subscripts now include y's and the acceleration is replaced with a g, for gravity.

Free Fall Demonstration

So, does mass have any affect on how fast an object falls? Watch this video demonstration for an answer. Be sure to set your volume at a reasonable level before you begin.


View the script

If you look at the equations dealing with free fall, mass is not a consideration!