Question
"A rock is dropped from the edge of a 180 m cliff. the function f(x) = -5t^2 - 5t + 180 gives the height of the rock, h(t), in meters t seconds after it was released. How long does it take for the rock to reach a ledge 80 m above the base of the cliff?"
I have no idea how to solve this, steps and explanations would be amazing.
I have no idea how to solve this, steps and explanations would be amazing.
Answers
well, since f(t) is the height of the rock at time t, just set it to 80 and solve for t:
-5t^2 - 5t + 180 = 80
5t^2 + 5t - 100 = 0
t^2 + t - 20 = 0
(t+5)(t-4) = 20
t=4
check:
f(4) = -5(16)-5(4)+180 = 80
-5t^2 - 5t + 180 = 80
5t^2 + 5t - 100 = 0
t^2 + t - 20 = 0
(t+5)(t-4) = 20
t=4
check:
f(4) = -5(16)-5(4)+180 = 80
W we tp
Related Questions
A person standing near the edge of a cliff 120 feet above a lake throws a rock upward with an initia...
1) A 20 kg rock is on the edge of a 100 m cliff.
a. What potential energy does the rock possess rel...
A rock is dropped off the edge of a cliff its distance S (in feet) from the top of the cliff after T...
A rock is dropped off the edge of the cliff and its distance S ( in feet ) from the top of the clif...