GPE and KE - Help with AS Physics Coursework

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In summary: At the point of release, however, the kinetic energy is maximized and the potential energy is minimized.
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meawinner
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GPE and KE...please help! argh

Hi I am just finishing my AS physics coursework and just as i thought i understood it someone tells me something else. When you pick up an object i understand that it gains GPE and the amount of this depends on the height it is picked up to, hence GPE = mgh. But when you drop the object what happens to the energy? Does it all suddenly convert to KE, or when it is falling does the GPE gradually turn to KE?

In my coursework i calculated GPE and KE, assuming they should be roughly the same values and they were but then some1 said to me that they should be inversely proportional to each other.

Can some1 please help me thank-you.

meawinner
 
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  • #2
just think about conservation of energy. when the object is falling, the height changes, by virtue of energy conservation, the object gains kinetic energy.
 
  • #3
If you lift a ball to some heigth h, you obtain a potential energy due to gravity that is equal to mgh. When the ball drops, the energy is gradually converted to KE, not all at once. To emphasize this point, imagine dropping the ball from heigth h. A friend catches the ball at height h/2. Since we already know the formula for potential energy due to gravity, our new potential would be equal to mgh/2. The ball still maintains an energy potential that was not converted to kinectic. All the potential energy is converted to kinetic energy at a time (only at the instantaneous moment right before impact) when h=0 after the point of release.
 
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  • #4
meawinner said:
In my coursework i calculated GPE and KE ...
some1 said to me that they should be inversely proportional to each other.
meawinner

As are implied by Dr Transport's and quantum mechanic's replies, the conversion of potential energy into kinetic energy (or vice versa in other situations) is a gradual process.

When we have energy conservation, it means that the SUM of kinetic energy and potential energy remains equal at all times.

Those who told you that the kinetic energy should be inversely proportional to the potential energy are totally wrong; they haven't learned the elementary distinction between a sum and a product.
 
  • #5
The sum of the energys must remain constant. (this is a no loss system of course!)

So Total Energy = Potential Energy + Kinetic Energy

This is true at each point of the fall.
 

1. What is the relationship between GPE and KE?

The relationship between gravitational potential energy (GPE) and kinetic energy (KE) is that GPE is a type of potential energy that is stored in an object due to its position in a gravitational field, while KE is the energy an object possesses due to its motion. As an object falls, its GPE is converted into KE. The higher the GPE, the more KE an object will have when it reaches the ground.

2. How do you calculate GPE and KE?

The formula for calculating GPE is GPE = mgh, where m is the mass of the object, g is the acceleration due to gravity (usually 9.8 m/s^2), and h is the height of the object from a reference point. The formula for calculating KE is KE = 1/2mv^2, where m is the mass of the object and v is its velocity.

3. How are GPE and KE related to each other?

GPE and KE are related to each other through the Law of Conservation of Energy, which states that energy cannot be created or destroyed, only transferred or converted. As an object falls, its GPE is converted into KE. At the bottom of the fall, the GPE will be zero and all of the energy will be in the form of KE.

4. Can GPE and KE be negative?

Yes, GPE and KE can be negative. This usually occurs when the reference point for GPE is below the object, or when an object is moving in the opposite direction of its initial velocity. However, the negative sign does not change the actual value of the energy, it just indicates the direction of motion.

5. How can understanding GPE and KE be helpful in real life?

Understanding GPE and KE can be helpful in real life in many ways. For example, understanding these concepts can help in designing roller coasters, calculating the potential and kinetic energy of a moving car, and understanding the energy transformations in a pendulum or a swinging object. It can also help in understanding the concept of potential and kinetic energy in different forms of energy, such as hydroelectric power or wind energy.

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