You accidental throw your car keys horizontally at 8.0 m/s from a cliff 64-m. high. How far from the base...?

Question

You accidentally throw your car keys horizontally at 8.0 m/s from a cliff 64-m. high. How far from the base of the cliff should you look for the keys.

Please help me with this problem.
I'm having trouble.

I previously asked this question, but was confused with the results I received.

Answer 1

First compute the fall time of the keys. Since you threw them horizontally, the fall is due only to gravity:

d=1/2*g*t^2
64=.5*9.8*t^2
t=sqrt(2*64/9.8)
once you have t, just multiply the horizontal velocity times the time of flight to get the distance traveled:

d=v*t
d=8*sqrt(2*64/9.8)
=29m

If you didn't understand how to compute the fall time, here's a bit more info:

The average velocity is
1/2*g*t
compute the fall distance as
1/2*g*t*t

j

Answer 2

ok first off, lets work out for the vertical component of the projectile...

since the car keys was thrown horizontally, initial vertical velocity is zero...

now, we need to find the final vertical velocity of the keys just before it hit the ground...

v^2 = u^2 + 2gs
v^2 = 0 + 2(9.8)(64)
v^2 = 1254.4
v = 35.417 m/s

now we need to find the time it took the keys to reach the ground...

v = u + gt
35.417 = 0 + 9.8t
t = 3.614s


now that we have the time, we can use the formula d = vt to find the horizontal distance from the base of the cliff...
(horizontal velocity remained constant throughout the flight)

d = vt
d = 8.0m/s * 3.614s
d = 28.91 m

therefore you need to look for the keys 28.91 meters from the base of the cliff...

here ya go...