Posted by Jackie on Tuesday, April 6, 2010 at 12:19am.
A rock is dropped of the side of a bridge and hits the water below 4s later.
a. What was the rock’s velocity when it hit the water?
b. What was the rock’s average velocity as it fell?
c. What is the height of the bridge above the water?

Physics  echem, Tuesday, April 6, 2010 at 12:26am
c. use kinematics equation
y=vi*t+1/2at^2
vi= 0 (because rock was dropped)
a=9.8m/s^2
t= 4s (time given)
plug in and you get your height
a. use kinematics equation
vf^2=vi^2+2ay
vi=0 (rock dropped)
a=9.8
y= (whatever you got from part c)
plug in and solve
b. ?

Physics  Fred, Tuesday, April 6, 2010 at 12:31am
To do this problem you just need to use a few simple equations:
V = V0 + at
X = X0 + V0*t + .5*a*(t^2)
and
V^2 = V0^2 + 2*a*(X  X0)
where V0 equals the initial velocity
X0 equals the initial height
t equals the time
a is just the acceleration (gravity in this case [9.81 m/s^2])
V is the final velocity
X is the final height
I think this should help you.
Answer This Question
Related Questions
 Physics  A rock is dropped from a bridge to the water below. It takes 2.40 s ...
 Physics  A rock is thrown horizontally from a bridge with a velocity of 13.0 m/...
 physics  A rock is dropped from a bridge to the water below. It takes 2.4s to ...
 physics  A rock is dropped from bridge to the water below. It take 2.4s to hit ...
 Physics 2701 Applied  A rock is thrown down with an initial speed of 30.0ft/s ...
 physics  a 2.00 lb rock is dropped from a bridge to the water 50 below. a. what...
 physics  A rock is dropped off of a bridge into the water below. If the initial...
 physics  A rock is thrown down with an initial speed of 10.0 m/s from a bridge...
 physics  a 2.00 kg rock is dropped from a bridge to the water 50.0m below. what...
 physics  A rock is dropped from rest off a cliff to the surface of a lake which...
More Related Questions