Potential energy and kinetic energy confusion

[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

 

[radou]

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.

 

[kyle8921]

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!