Physics
posted by Phil on .
A person throws a ball upward into the air with an initial velocity of 15.0 m/s.
Calculate the following:
a.) how high it goes.
b.) how long the ball is in the air before it comes back to his hand.
c.) at what time(s) will the ball pass a point 8.00 m.
If you got multiples times, are both solutions valid? Why or why not?

a. h = (Vf^3  Vo^2) / 2g,
h = (0  (15)^2) / 19.6 = 11.5m.
b. t(up) = (Vf  Vo) / g,
t(up) = (0  15) / 9.8 = 1.53s.
t(dn) = t(up) = 1.53s.
T = t(up) + t(dn) = 1.53 + 1.53 = 3.06s. = Time in flight.
c. d = Vot + gt^2 = 8m,
15t 4.9t^2 = 8,
4.9t^2 + 15t 8 = 0,
Use Quadratic Formula to find t:
t = 0.69s.