Quadratic Equation
ax  bx  c  0
2
 b  b  4ac
x
2a
2
1
1. A baseball is thrown upward with speed
10m/s from a height of 2m above ground.
How long is it in the air before striking
ground?
y  vot  a yt
1
2
2
 2  10t  (9.8)t
1
2
 2  10t  4.9t
2
4.9t  10t  2  0
2
2
4.9t  10t  2  0
2
10  (10) 2  4(4.9)( 2)
t
2(4.9)
 b  b 2  4ac
2a
10  100  39.2
t
9.8
10  11.8
t
9 .8
t  2.22s or -0.18s
With what speed does the ball hit the
ground?
v  vo  at
v  10m / s  (9.8m / s / s)( 2.22s)
v  10m / s  (21.8m / s)
 11.8m / s
(11.8m/s, downward)