A ball is dropped from a building 96 ft tall. The height of the ball after t seconds is measured by the function h(t) = −16t^2 + 96, where h(t) is measured in feet and t is time in seconds.

How long will it take the ball to fall to 32 feet?

Question

A ball is dropped from a building 96 ft tall. The height of the ball after t seconds is measured by the function h(t) = −16t^2 + 96, where h(t) is measured in feet and t is time in seconds.

How long will it take the ball to fall to 32 feet?

turingtest · Answer

h(t)=32=-16t^2+96
16t^2-64=0
t^2-4=0
t=2 sec

phi · Answer

double post?

replace h(t) with 32 feet
32= -16t^2 +96
or
16t^2= 96-32
16t^2= 64
t^2= 64/16
can you finish?

turingtest · Answer

hey @phi, you think they mean h(t)=96-32?

phi · Answer

@turing: you did it right.

turingtest · Answer

I thought maybe they mean if it falls 32 feet it is at height 96-32=64
64=-16t^2+96
16t^2-32=0
t=sqrt(2)

phi · Answer

How long will it take the ball to fall *to* 32 feet
which I interpret as h(t)= 32.  h(0)= 96, which is where it starts.