Problem in understaning potential energy

• Vatsal Goyal
In summary: No. The work done by the engine is the difference between the initial energy of the engine and the final energy of the car. The engine is providing the car with kinetic energy.The work done by the engine is the difference between the initial energy of the engine and the final energy of the car.
Vatsal Goyal

Homework Statement

If we lift a block with constant velocity, by applying a force mg upwards, is the work done zero?

The Attempt at a Solution

The work done must be zero as the resultant force is zero, what I don't understand is how does the block get potential energy if no work is being done?

I assume that m is the mass of the block.

Why do you think that it should gain potential energy?

You should write down some relevant equations and show some work if you want any hints.

FactChecker said:
Why do you think that it should gain potential energy?
It should gain some energy, as when we will release the block, the block will gain kinetic energy, indicating it must have had some form of energy at the height which is converted into kinetic energy.

Vatsal Goyal said:

Homework Statement

If we lift a block with constant velocity, by applying a force mg upwards, is the work done zero?
The work done by all forces is zero, that means the KE does not change (work-energy theorem).
Vatsal Goyal said:

The Attempt at a Solution

The work done must be zero as the resultant force is zero, what I don't understand is how does the block get potential energy if no work is being done?
How is the potential energy of a body at a point due to a force defined?

Vatsal Goyal said:
It should gain some energy, as when we will release the block, the block will gain kinetic energy, indicating it must have had some form of energy at the height which is converted into kinetic energy.
The block has some potential energy initially due to the height that it starts at.. Do you think that the force increases it? If so, why?

ehild said:
How is the potential energy of a body at a point due to a force defined?
It is defined as the energy a body has due to its position or configuration, and measured by the work that could be done by a body passing from its present position to some zero position.

FactChecker said:
The block has some potential energy initially due to the height that it starts at.. Do you think that the force increases it? If so, why?
Yes, I think it would, suppose the block is at height h in the beginning. We lift it by a distance x with velocity u. Now, if we drop it, when it reaches height h, it will have velocity v>u as only force of gravity is acting on it, hence total energy at h is greater than what it was before, then at height h+x, it must have had some extra energy, which is giving the extra kinetic energy at h.

Vatsal Goyal said:
It is defined as the energy a body has due to its position or configuration, and measured by the work that could be done by a body passing from its present position to some zero position.
Potential energy due to a conservative force is defined as the work done by that force when the body passing from its present position to the position of zero potential energy.

Delta2
Vatsal Goyal said:
Yes, I think it would, suppose the block is at height h in the beginning. We lift it by a distance x with velocity u. Now, if we drop it, when it reaches height h, it will have velocity v>u as only force of gravity is acting on it, hence total energy at h is greater than what it was before, then at height h+x, it must have had some extra energy, which is giving the extra kinetic energy at h.
Yes. The first step is to calculate the values of x and u. They may be positive, negative, or zero.

Vatsal Goyal said:

Homework Statement

If we lift a block with constant velocity, by applying a force mg upwards, is the work done zero?

The Attempt at a Solution

The work done must be zero as the resultant force is zero, what I don't understand is how does the block get potential energy if no work is being done?

Consider a car moving at constant 100mph on level ground. The net force acting on the car is also zero (it's not accelerating or decelerating). Do you think the engine is doing zero work?

What is potential energy?

Potential energy is the energy possessed by an object due to its position or state. It is stored energy that has the potential to do work.

How is potential energy different from kinetic energy?

Potential energy is the energy of an object at rest, while kinetic energy is the energy of an object in motion. Potential energy can be converted into kinetic energy and vice versa.

What are the different types of potential energy?

There are several types of potential energy, including gravitational potential energy, elastic potential energy, chemical potential energy, and nuclear potential energy.

How can potential energy be calculated?

The formula for potential energy varies depending on the type of potential energy. For example, gravitational potential energy can be calculated using the formula 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. Elastic potential energy can be calculated using the formula PE = 1/2kx^2, where k is the spring constant and x is the displacement from equilibrium.

Why is understanding potential energy important?

Understanding potential energy is important because it helps us understand how energy is stored and transferred in different systems. It is also essential in various fields such as physics, engineering, and chemistry, and is the basis for many real-world applications such as energy storage and conservation.

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