# Mechanical Energy: Kinetic & Potential Energy Balance

• wolves5
In summary, the total mechanical energy of a system is constant as long as only conservative forces act on it. This means that it is either split equally between kinetic energy and gravitational potential energy (choice A) or it can be solely kinetic energy or solely gravitational potential energy at any given time (choice C). However, it cannot be determined for most naturally occurring systems (choice D). It is important to consider past examples and use logical arguments to determine which option is correct, as a single counterexample can disprove a proposition.
wolves5
1. The total mechanical energy of a system:

a. is split equally between kinetic energy and gravitational potential energy.
b. is constant as long as only conservative forces act on it.
c. is either only kinetic energy or only gravitational potential energy at any given time.
d. cannot be determined for most naturally occurring systems.

For this question, I think the answer is A. This is because Total Mechanical Energy is eqaul to Potential Energy + Kinetic Energy. Is my reasoning right?

So, you're proposing that KE is always equal to PE?

Yes..isnt that right?

In all the projectile problems that you've worked on, was potential energy always (at all times) equal to kinetic energy? Even, for example, when a vertically launched projectile is at the top of its trajectory?

Oh no it wasnt the same. So since its not split equally, it would be C then?

wolves5 said:
Oh no it wasnt the same. So since its not split equally, it would be C then?

I think that you should reflect on the problems that you've done involving PE and KE and try to draw logical arguments for accepting or rejecting the provided choices. Remember, a single counterexample disproves a proposition.

I'm not going to answer your question for you by eliminating or confirming them one at a time when you say something like, "Is it C?"

## 1. What is mechanical energy?

Mechanical energy is the energy possessed by an object due to its motion or position.

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

Kinetic energy is the energy an object has due to its motion, while potential energy is the energy an object has due to its position or state.

## 3. How does mechanical energy change from kinetic to potential and vice versa?

When an object is in motion, its mechanical energy is primarily in the form of kinetic energy. As the object moves and changes position, some of the kinetic energy is converted into potential energy. For example, when a ball is thrown into the air, it starts with high kinetic energy and as it reaches the highest point, it has maximum potential energy. As it falls back down, potential energy is converted back into kinetic energy.

## 4. How is mechanical energy conserved in a closed system?

In a closed system, mechanical energy is conserved, meaning it cannot be created or destroyed. It can only be converted from one form to another. For example, in a pendulum, as the pendulum swings back and forth, the kinetic energy and potential energy are constantly changing, but the total mechanical energy remains the same.

## 5. How is mechanical energy used in everyday life?

Mechanical energy is used in many everyday activities such as riding a bike, driving a car, or playing sports. It is also used in machines such as elevators, roller coasters, and simple tools like a lever or pulley. In renewable energy, mechanical energy is converted into electrical energy in wind turbines and hydroelectric power plants.

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