The ball was 3 feet off the ground when she struck it with an initial upward velocity of 24 feet per sec. The equation I have to use is h=-16t^2+vt+h(sub zero)

Question

I need help quick! I have to use the equation to write an equation to model the scenario.

Answer 1

Anna,

The equation you have to use comes from the standard equation:

Δx = Δx₀ + v₀ t + ½ a t²

where Δx₀ is initial displacement
v₀ is the initial velocity
a is acceleration and
t is elapsed time after she struck the ball.

 

a is g in your case and g is 9.8 m/s² which is 9.8 m/s² x 3.28 ft/m = 32 ft/s²  ==> ½ a t² = 16t²

 

since g is always downward to the center of the Earth,

so if you set upward as +, then ½ a t² = 16t² is negative  ==> -16t²

 

v₀ is the velocity which is upward ==> +

 

I hope this help you understand why you HAVE to use the equation given.

 

Now put it a lot of t values (may be from t = 0, 1, 2, 3, 4, 5, 6, 7.....) and 

compute the corresponding h values and set a two column table to store them.

 

Then plot a graph of h vs. t.  Like Dave said, you will get a parabola.  

 

HIH!

 

Best!

 

Dr. Jonathan Y