Molly throws a softball straight up with an initial velocity of 20 ft/s. The release point is 5 ft above the ground. After how many seconds will the softball hit the ground?

Answer 1

Givens:

v_i=20ft/s

h_i=5ft

a=g=-9.81m/s²

h=0

Equations:

h=1/2at²+v_it+h_i

Sometimes is written with x, y, or s instead of h,

Plug in:

h=1/2at²+v_it+h_i

0=1/2(-9.81)t²+20t+5

Use quadratic formula

t=(-20±√(20²-4(1/2(-9.81)(5))))/(-9.81)

t=-0.24s or t=4.3s

Since the ball cant land before you throw it, the negative time is invalid so t=4.3s