Question

A rock falls from a tower that is 400 ft high. As it is falling its height is given by the function h(t)=400-16t^2. Ho many seconds will it take for the rock to hit the ground (h=0)?

Answer 1

set \[h(t)=400-16t^2=0\] solve for t

Answer 2

since h =0 when it touches the ground
400-16t^2=0
16t^2=400
t^2=400/16
t^2= 25
t=5 seconds

Answer 3

\[0=400-16t^2\]
\[16t^2=400\]
\[t^2=25\]
\[t=5\]

Answer 4

oh. i see thank you