# Potential energy and kinetic energy confusion

• roxas
In summary, the conversation discusses the concept of energy in relation to a rollercoaster. The maximum energy of the rollercoaster is 4000j, with a mass of 20kg and an acceleration due to gravity of 10m/s^2. The individual is trying to calculate the velocity at a specific point, but is confused by the process. They question why the potential energy is subtracted from the total energy to find kinetic energy, instead of being added. Ultimately, the conversation highlights the relationship between kinetic and potential energy in terms of conservation.
roxas
okay this question is confusing like everything i currently know about p.e and k.e.
okay so the maximum energy of a rollercoaster is 4000j. the mass of the trolly is 20kg, and the acceleration due to gravity is 10m/s^2(dunnoe where's the squared button on the keyboard) okay so i am supposed to calculate the velocity at this point. my teacher gave the working for this answer and he minus the potential energy from the total energy to find the k.e, and this is where i got confused. isn't the potential energy lossed =the gain of K.E? why did he minus the P.E from the T.E? help! my physics practical is a day away and i can't afford to be confuzzled.

by the way i didnt clarify this wif my teacher as i was daydreaming in class and just copied down the answer. thx

The total energy consists of kinetic and potential energy, as you know already. Since total energy is conserved, maximizing kinetic energy must minimize potential energy, and vice versa. So, an object has its maximal kinetic energy when its potential energy is minimal. The same holds for maximal potential energy.

Hi there,

I understand that you are confused about the relationship between potential energy and kinetic energy, and how they are used to calculate the velocity of a rollercoaster. Let me try to clarify this for you.

First, let's define potential energy and kinetic energy. Potential energy is the stored energy an object has due to its position or state, while kinetic energy is the energy an object has due to its motion. In the case of a rollercoaster, when it is at the top of a hill, it has a lot of potential energy because of its height. As it moves down the hill, this potential energy is converted into kinetic energy, which is why it speeds up.

Now, in order to calculate the velocity at a certain point, we need to use the principle of conservation of energy. This means that the total energy at one point is equal to the total energy at another point. In the case of a rollercoaster, the total energy is the sum of its potential energy and kinetic energy.

So, when your teacher subtracted the potential energy from the total energy, it was to find the remaining energy, which is the kinetic energy. This is because the potential energy is converted into kinetic energy as the rollercoaster moves down the hill. It is not a loss of potential energy, but a conversion into kinetic energy.

I hope this helps to clarify things for you. Remember to always ask your teacher for clarification if you are unsure about something. Good luck on your physics practical!

## 1. What is the difference between potential energy and kinetic energy?

Potential energy is the energy stored in an object due to its position or state, while kinetic energy is the energy an object possesses due to its motion.

## 2. How are potential energy and kinetic energy related?

Potential energy can be converted into kinetic energy and vice versa. When an object is at rest, it has potential energy, and when it is in motion, it has kinetic energy.

## 3. Can potential energy be negative?

Yes, potential energy can be negative. This usually occurs when the reference point for measuring potential energy is below the object's position.

## 4. Why is it important to understand the difference between potential energy and kinetic energy?

Understanding the difference between potential energy and kinetic energy is crucial in many areas of science and engineering. It helps us understand how energy is stored and transferred in various systems, such as in machines, chemical reactions, and natural phenomena like weather and tides.

## 5. How can potential energy and kinetic energy be calculated?

The formula for potential energy is PE = mgh, where m is the mass of the object, g is the acceleration due to gravity, and h is the height of the object. The formula for kinetic energy is KE = 1/2mv^2, where m is the mass of the object and v is its velocity. Both potential energy and kinetic energy are measured in joules (J).

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