In general, the height of a projectile is given by
[tex]h= -\frac 1 2 g t^2 + v t + h_0[/tex]
where [tex]h[/tex] is the height at time [tex]t[/tex] of a projectile shot upward at velocity [tex]v[/tex] from initial height [tex]h_0[/tex].
The acceleration of gravity [tex]g= 9.8 \textrm {m/s}^2 \textrm{ or } g=32\textrm{ feet/s}^2.[/tex] We give it a negative sign in the equation because it pulls down.
Let's apply it to each group.
Group A launches a tennis ball straight up with an initial velocity of 19 meters per second.
We have MKS units, positive (upward) velocity and an initial height of 0.
[tex]h= -\frac 1 2(9.8) t^2 + (19) t + 0 = -4.9t^2 + 19t[/tex]
Group B launches a tennis ball straight up with an initial velocity of 50 feet per second. Not metric, velocity +50, initial height zero.
[tex]h= -16t^2 + 50t[/tex]
Group C drops a tennis ball from a height of 19 meters.
MKS, initial height 19, initial velocity zero.
[tex]h= -\frac 1 2 g t^2 + v t + h_0 = -4.9 t^2 + 19[/tex]
Group D drops a tennis ball from a height of 50 feet.
[tex]h= -16 t^2 + 50[/tex]
