math
posted by kaley on .
recall that the acceleartion due to earth's gravity is 32 ft/sec^2. from ground level, a projectile is fired straight upward with velocity 90 feet per second.
a. what is its velocity after 3 seconds
b. when does it hit the ground
c. when it hits the ground, what's the net distance it has traveled.
d. when it hits the ground, what is the total distance it has traveled

a) use v = Vo  gt
b ) use equation in part a to find out when v = 0. At that point the thing is as high as it will go. It will spend the same time falling so double the time you found for ascent to find out when it hits the ground.
c) LOL it came right back to where it started if you shot straight up :)
d) we know how long it took to get to the top (half of the final answer in part b)
so how far up did it go?
Y = Yo + Vo t +(1/2) a t^2
Y = 0 + 90 t  16 t^2 where t is half the total time aloft from part b
double that answer to include the distance it fell. 
simplifing fractions

alyssa in general factor top and bottom and cancel like factors
for example 12 /16
= 2*2 *3

2*2 *2*2
so it is really 3/4