MATHEMATICAL MODEL OF MOTION
Definitions of each of the variables you see above:
= This is the final velocity (or velocity of impact) (units = m/s)
= This is the initial velocity.
Use a positive (+) value if you initially throw something up.
Use a negative value (-) if you initially throw something down (units = m/s)
If the initial velocity is zero (v0
= 0), you can
remove it from the equation.
= acceleration. When
solving problems using gravity, substitute g for a
(remember g is a constant at -9.8
m/s2) This is
because gravity always acts downward. (units
= final distance. In the problems
involving objects dropped, etc., d
will represent the displacement in the y-direction.
It is positive (+) if the final position is above where you threw it.
It is negative (-) if the final position of the object is below where
your threw it. (units = m)
= initial distance. This is where
the object started. This value is
very often = 0 (d0 = 0).
In this case, you can remove it from the equation. (units = m)
= This the time the object is in motion. It
is always positive. If you find it
to be negative, then you did something wrong!
(units = s)
t0 = This the initial time the object was put in motion. Yes I know, you do not see this in any of the equations above. That is because it was assumed in each that t0 = 0, and was therefore eliminated from the equation. REMEMBER → we arrived at each of the equations above from our two favorite equations of average velocity and average acceleration !
when solving the kinematics motion problems, always follow these
H E Y ! M R . W I L S O N
Website by Duncan Wilson
Page last updated January 07, 2012