Gravitational Potential Energy

In summary: So, you are using energy, but not doing work.In summary, the conversation discusses the concept of force and weight in relation to lifting objects. It is emphasized that the force applied does not need to be greater than the weight of the object, as long as it is equal, the object will move upwards at a steady speed. Examples are provided, such as riding an escalator, to illustrate this concept. It is also mentioned that friction and stiction can affect the movement of objects and require a small excess of force. Before Newton, people believed that everything naturally slows down, but now it is understood that work is required to maintain the movement of an object.
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averycasille
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Hello, I do not quite get this. Can anyone provide examples?
" We may feel that it takes a force greater than the weight of the object being raised to lift it upwards, but it is not so. Provided the force is equal to the weight, the object will move upwards at a steady speed. "
 
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  • #2
averycasille said:
Hello, I do not quite get this. Can anyone provide examples?
" We may feel that it takes a force greater than the weight of the object being raised to lift it upwards, but it is not so. Provided the force is equal to the weight, the object will move upwards at a steady speed. "
If you are riding an escalator upward, you feel the ordinary force of gravity. Your feet push down on the escalator with your normal weight and the escalator supports you by exerting an equal and opposite upward force.

Of course, when you step onto the escalator there must be a momentary increased upward push and when you step off, there must be a momentary decreased upward push.
 
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  • #3
averycasille said:
Hello, I do not quite get this. Can anyone provide examples?
" We may feel that it takes a force greater than the weight of the object being raised to lift it upwards, but it is not so. Provided the force is equal to the weight, the object will move upwards at a steady speed. "
I agree that this is not totally intuitive. I think that your problem is because in any practical situation there is friction (and stiction), which will 'naturally' slow things down and would require some small excess of upward force over the weight for the mass to keep rising. Plus, to accelerate the object in the first place, will require an excess force. Before Newton, people believed that everything naturally slows down, which was not totally unreasonable, in a world where even wheeled vehicles slowed down on the level, due to rubbish bearings and road surfaces. They believed that the Planets were being pushed around, for the same reason.
Also, you have to keep pushing (to compensate for the loss in Gravitational Potential Energy.
 

Related to Gravitational Potential Energy

1. What is gravitational potential energy?

Gravitational potential energy is the energy that an object has due to its position in a gravitational field. It is the potential energy stored in an object when it is lifted to a certain height above the ground.

2. How is gravitational potential energy calculated?

The formula for calculating gravitational potential energy is PE = mgh, where PE is the potential energy, m is the mass of the object, g is the acceleration due to gravity, and h is the height of the object above the ground.

3. What factors affect gravitational potential energy?

The factors that affect gravitational potential energy include the mass of the object, the height of the object above the ground, and the strength of the gravitational field.

4. How is gravitational potential energy related to kinetic energy?

Gravitational potential energy and kinetic energy are directly related. As an object falls, its potential energy decreases and its kinetic energy increases. At the bottom of the fall, all of the potential energy has been converted into kinetic energy.

5. Can gravitational potential energy be negative?

Yes, gravitational potential energy can be negative. This happens when the reference point for measuring potential energy is below the object's starting position. In this case, the potential energy is negative because the object has already lost some of its potential energy due to its position in the gravitational field.

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