Question

An rock is thrown downward from a platform that is 247 feet above ground at 75 feet per second. Use the projectile formula

h
=
−
16
t
2
+
v
0
t
+
h
0
to determine when the rock hit the ground.

[Recall that
v
0
is the initial velocity of the object and
h
0
is the inital height of the object.]

Answer: The rock will hit the ground after

Select an answer

Answer 1

-16t² - 75t + 247 = 0

16t² + 75t - 247 = 0

t = (-75 + √(75² - 4(16)(-247))/32

= (-75 + √21,433)/32

= (-75 + 146.4)/32

= 2.23 seconds

The rock will hit the ground after 2.23 seconds.