Register to reply

Time for an object to fall

by jamesd2008
Tags: fall, object, time
Share this thread:
jamesd2008
#1
Apr25-10, 06:06 PM
P: 64
Hi,

If you no the height of an object only, assuming no frictional forces, and that it is on earh. Can you determine how long it will take to hit the ground?

Thanks
James
Phys.Org News Partner Physics news on Phys.org
Physicists unlock nature of high-temperature superconductivity
Serial time-encoded amplified microscopy for ultrafast imaging based on multi-wavelength laser
Measuring the smallest magnets: Physicists measured magnetic interactions between single electrons
jamesd2008
#2
Apr25-10, 06:08 PM
P: 64
Also the final velocity is also unknown and the initial velocity is zero?
karkas
#3
Apr25-10, 07:45 PM
P: 125
I am assuming that you're talking about the height between the object and the floor. The answer is yes, and that is obvious from the equations that describe free fall, meaning the fall that is induced and preserved only by the force of gravitational attraction that the earth exerts on the body.

So we have
[itex]h = \frac{1}{2} g t^2 \Leftrightarrow t = \sqrt{\frac{2h}{g}} [/itex]
and since you know h, you can calculate the required time. Using that t you can solve for the final velocity of the body, the one it has right before it reaches ground. And yes, since you let the body go at one point without pushing it downwards, the initial velocity is zero.

morrobay
#4
Apr25-10, 09:53 PM
P: 375
Time for an object to fall

Quote Quote by karkas View Post
I am assuming that you're talking about the height between the object and the floor. The answer is yes, and that is obvious from the equations that describe free fall, meaning the fall that is induced and preserved only by the force of gravitational attraction that the earth exerts on the body.

So we have
[itex]h = \frac{1}{2} g t^2 \Leftrightarrow t = \sqrt{2gh} [/itex]
and since you know h, you can calculate the required time. Using that t you can solve for the final velocity of the body, the one it has right before it reaches ground. And yes, since you let the body go at one point without pushing it downwards, the initial velocity is zero.
No t=square root (2h/g)
velocity = square root (2gh)
karkas
#5
Apr26-10, 06:40 AM
P: 125
Yes sorry my bad.
jamesd2008
#6
Apr26-10, 09:49 AM
P: 64
Thanks for the reply's guys, much help


Register to reply

Related Discussions
How Long Does it Take An Object To Fall 5 m From Rest? Introductory Physics Homework 1
At what angle does an object fall off a sphere? Introductory Physics Homework 3
Why doesn't an object fall through the ground when it hits it? General Physics 9
What speed will an object fall? Classical Physics 5
Fall of Object Introductory Physics Homework 4