Author Question: How to calculate the time it takes for an object to go from its maximum height it its landing position? (Read 3007 times)

xclash

  • Hero Member
  • *****
  • Posts: 681
I totally don't understand how to calculate this. Hint: Use potential energy calculation (PEgravitational=mgh) m=mass, g=gravitational field pull (9.8) and h=height, estimated mass, and kinetic energy formula (KE=.5mv^2). I'll try figuring this out again, but it's a problem I've been stuck on! Thank you in advance!



frankwu

  • Hero Member
  • *****
  • Posts: 549
OK:

At its maximum height, assume the object is not moving up or down.  The object posseses

(1)  PE = mgh

When it hits the ground, it will have lost all its PE, which will have been converted into KE:

(2)  KE = .5*mv^2

The force acting on the object as it falls is

(3)  F = ma, where the "a" represents acceleration imparted to m when the force F on it is converted into motion.  In the context of the earth's gravity, the "a" is what we symbolize by g:

(4)  F = mg,  where

 g  = 9.8 m/s^2 = 9.8 (m/s)/s, (meters per second) per second.

Velocity is meters/second, and acceleration is the rate of change in velocity, or velocity/second.

If you know the acceleration, then you know the velocity after t seconds:

(5)  v = gt

Putting all of the above together:

(6)  mgh = .5*mv^2      since KE = PE at impact.  Substituting for v from (5), we get

(7)  mgh = .5 * m * (gt)^2  = .5 * m * g^2 * t^2  

Canceling terms common to each side, we get:

h = .5 * g * t^2

Rearranging and solving for t, we get

(8)  t = ?(2h / g)   <<---ANSWER

Notice that the time is not dependent on the mass.
.



Related Topics

Need homework help now?

Ask unlimited questions for free

Ask a Question
 

Did you know?

Between 1999 and 2012, American adults with high total cholesterol decreased from 18.3% to 12.9%

Did you know?

Human neurons are so small that they require a microscope in order to be seen. However, some neurons can be up to 3 feet long, such as those that extend from the spinal cord to the toes.

Did you know?

When taking monoamine oxidase inhibitors, people should avoid a variety of foods, which include alcoholic beverages, bean curd, broad (fava) bean pods, cheese, fish, ginseng, protein extracts, meat, sauerkraut, shrimp paste, soups, and yeast.

Did you know?

In 2006, a generic antinausea drug named ondansetron was approved. It is used to stop nausea and vomiting associated with surgery, chemotherapy, and radiation therapy.

Did you know?

Famous people who died from poisoning or drug overdose include, Adolf Hitler, Socrates, Juan Ponce de Leon, Marilyn Monroe, Judy Garland, and John Belushi.

For a complete list of videos, visit our video library