a 12 kg rock falls from rest off a cliff and hits the ground in 1.5 seconds.
~ignoring air resistance, what is the rocks velocity just before it hits the ground?
~what will the rocks weight be after it hits the ground?
PLEASE HELP!!!!!!!!!!!
2007-05-07 12:05:31 · 7 answers · asked by Emily 2 in Education & Reference ➔ Homework Help
I get:
It falls 11.025m
It's velocity just before hitting the ground is 14.7m/s
To solve you simply need
Distance x = (1/2) * a * t^2 + v(0)* t + x(0)
Where a is acceleration, t is time, v(0) is the initial velocity, and x(0) is the initial starting point.
Velocity's equation is v = a * t + v(0) where a = acceleration, t is time, and v(0) is initial velocity.
Velocity before hitting ground v = 9.8m/s^2 * 1.5 sec + 0 = 14.7m/s
As many have said weight is simply m*g = 12kg * 9.8m/s^2 = 117Newtons
Don't know why people are converting to english units but Amy W's answers for velocity is correct in English units, but her answer of 12kg is a unit of mass, not weight.
2007-05-07 12:18:26 · answer #1 · answered by hsueh010 7 · 0⤊ 0⤋
If the height of the cliff in feet is x, the height of the rock at time t seconds is x-16t^2. So the cliff is 36 feet high. (Which now I see you didn't ask. Oh well.)
Velocity is the derivative of the height, -36t. Since t is 1.5 seconds, the velocity of the rock is -36*1.5=-54. So it is traveling downward at 54 feet per second when it hits the ground.
After the rock hits the ground, it will weigh 12 kg.
2007-05-07 19:20:20 · answer #2 · answered by Amy W 6 · 0⤊ 0⤋
Well hopefully you have some kind of equation for the first part. As for the second part, the rock should weigh the same after it hits the ground... I mean you would weigh the same even if you fell off a cliff...
2007-05-07 19:09:02 · answer #3 · answered by oxymoron1992 2 · 0⤊ 0⤋
The rocks weight will actually change a little bit because of its distance from the center of the Earth has changed. But this is so small that usually, it's negligible. So, effectively, you can say that the weight of the rock is the same.
2007-05-07 19:10:53 · answer #4 · answered by Traqqer 2 · 0⤊ 0⤋
if this is on earth, the answer is equal to the force of Earth's gravity. In other words, if there was no such thing as wind resistance, all items will fall back down to earth at Earth's gravity yield.
This is equal to 9.8 meters per second.
I've provided a supportive and informational link below...
2007-05-07 19:12:53 · answer #5 · answered by xgritsx 2 · 0⤊ 0⤋
Force = mass x acceleration
velocity = initial velocity + (acceleration x time)
(Force is like weight)
now plug away ! hint :initial velocity = zero and acceleration = 9.8 m/sec2
hope that's correct .
2007-05-07 19:18:26 · answer #6 · answered by CHRISTOPHER C 4 · 0⤊ 0⤋
65 ft/sec
12 kg
2007-05-07 19:10:52 · answer #7 · answered by Anonymous · 0⤊ 0⤋