Formula for Gravity
Date: 9/2/96 at 19:48:17 From: Anonymous Subject: Formula for gravity Hi! My name is Eric. I am curious if there is a way to figure out the force of gravity on an object. For example, if I throw a ball straight up in the air at 40 miles an hour, how long will it take for the ball to come down? Thanks a lot.
Date: 9/5/96 at 9:59:19 From: Doctor Jerry Subject: Re: Formula for gravity Hi, Eric. Galileo and Newton figured out how to answer this question about 400 years ago. To make the problem easier, they decided to ignore the resistance of the air. It's possible to work out the time it takes for the ball to come down in air, but the calculation is quite a bit harder. So, if you don't mind too much, I'll give the easier answer. Galileo and Newton said that the force of gravity on an object is proportional to the acceleration it causes. At the earth's surface, the acceleration of the object due to the earth's pull is about 32 feet per second per second. To answer your question, I'll assume that you are asking how long it takes for the ball to return to the same height from which it was released at 40 mph. All you have to do is to divide the initial velocity (expressed in feet per second) by 32/2 = 16. Can you convert 40 miles per hour to feet per second? The calculation is 40 * 5280 / 3600 = 58 and 2/3 feet per second. So, divide 58 and 2/3 by 16 to find out how long it takes for the ball to come down (in a vacuum). I hope this answers your question. -Doctor Jerry, The Math Forum Check out our web site! http://mathforum.org/dr.math/
Search the Dr. Math Library:
Ask Dr. MathTM
© 1994- The Math Forum at NCTM. All rights reserved.