How is 1N enough to move a 0.1kg apple 1 meter high?

In summary, an apple requires 1 Newton of force to hold it against gravity. To lift it 1 meter, it takes 1 J of energy.
  • #1
M3D1
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Example: How much energy is needed to lift an 0.1 kg apple up 1 meter?​

gravity apple force


To hold a 0.1 kg apple against gravity needs 1 Newton of force:
F = mg
F
= 0.1 kg × 9.8 m/s2
F
1 N
But holding an apple is not work, the apple needs to move!

So, raising it using 1 N for 1 m (both in same direction!) gives:

Work = 1 N × 1 m × cos 0° = 1 J
‐--------‐-----‐------------
i am confused in that if 1N only holds the apple (since the force of gravity and my hand add up zero net force to apple) then how does apple moves up 1 meter by just 1N to a 1 meter distance to result in one J of energy. i don't know whether i misunderstood the concept of work or misunderstood sth about question .
thanks in advance for any help i could recieve
 
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  • #2
M3D1 said:
i am confused in that if 1N only holds the apple (since the force of gravity and my hand add up zero net force to apple) then how does apple moves up 1 meter by just 1N to a 1 meter distance to result in one J of energy.
I think what you're asking is how can exerting exactly 1 N of force actually lift the apple. If you start from rest, you have a good point. To start things moving you must at least exert a little more force than just enough to balance gravity! But the work you have to do against gravity is still just what you calculated. Any additional work you do goes to increasing the kinetic energy of the apple.
 
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  • #3
If you apply a teeny tiny force greater than 1 N for a very short time to get the apple moving up and then reduce the force to exactly 1 N, the apple will keep on moving up at constant speed. When you get to 1 m higher, reverse the process to stop the apple and keep it there. The apple is still at rest, the change in kinetic energy is zero, the average force exerted by your hand is 1 N and the apple is 1 m higher than it was. The (positive) work done by your hand on the apple is equal to the change in potential energy of the apple plus Earth system.

On edit: I see that @Doc Al preempted me with essentially the same answer.
 
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  • #4
Well, whatever the ups and downs of the apple, if it starts at rest and ends at rest ##1m## higher, then it has gained ##1J## of potential energy.

How it got there we can leave to those with a flair for engineering problems.
 
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  • #6
If it takes 0.98 N to hold the apple in place against gravity, and you apply 1.00 N, so you will have an excess force of 0.02 N.
Since, F = m⋅a ; the apple will accelerate upwards, with; a = 0.02 N / 0.1 kg .
Given enough time, the apple could reach escape velocity.
 
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  • #7
Baluncore said:
If it takes 0.98 N to hold the apple in place against gravity, and you apply 1.00 N, so you will have an excess force of 0.02 N.
Since, F = m⋅a ; the apple will accelerate upwards, with; a = 0.02 N / 0.1 kg .
Given enough time, the apple could reach escape velocity.
LOL. :-p

I'm sure the intention was to exert just enough upward force to balance the gravitational force on the apple. (But you are correct.)
 
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  • #8
M3D1 said:
i don't know whether i misunderstood the concept of work
You do not misunderstand the concept. As you prove by writing
M3D1 said:
But holding an apple is not work

The everyday experience that you get tired from holding up a bag of apples does not mean that it is work in the physics sense: a shelf or a hook on the wall can do exactly the same job and does not have to be provided with energy to do it.

But lifting a bag of apples from a lower shelf to a higher one does require work. Lifting the weight of an old fashioned clock requires work. The work (energy) that can run the clock for a while.

##\ ##
 
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  • #9
I think the concept of a conservative force field is important here. The gravitational force field is conservative. This essentially means that if you move something from location A to location B in that field, the energy used to get from A to B only depends on the field potential (height above ground in this case), and not on the path taken. This means that the amount of energy only depends on the height difference.
 
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Related to How is 1N enough to move a 0.1kg apple 1 meter high?

1. How is 1N enough to move a 0.1kg apple 1 meter high?

1N (Newton) is the unit of measurement for force, which is defined as the amount of energy required to move an object with a mass of 1kg at a rate of 1 meter per second squared. In this case, the 1N force is being applied to a 0.1kg apple, which is 10 times lighter than the standard 1kg object. This means that the 1N force is more than enough to move the apple 1 meter high.

2. What other factors contribute to the apple being moved 1 meter high?

In addition to the 1N force, there are other factors that contribute to the apple being moved 1 meter high. These include the angle at which the force is applied, the surface on which the apple is placed, and the amount of friction present. These factors can affect the amount of energy needed to move the apple and the distance it will travel.

3. How does the force of gravity affect the movement of the apple?

The force of gravity plays a significant role in the movement of the apple. It is constantly pulling the apple towards the ground, which creates a downward force that must be overcome by the 1N force applied. As the apple moves upwards, the force of gravity decreases, allowing the apple to reach a height of 1 meter before falling back to the ground.

4. Can 1N move the apple higher than 1 meter?

It is possible for 1N to move the apple higher than 1 meter, but it would require more time and energy. This is because the force of gravity increases as the apple moves higher, making it more difficult to overcome. Additionally, other factors such as air resistance and the apple's shape can also affect its movement.

5. How does the concept of work relate to the movement of the apple?

Work is defined as the product of force and distance, and it is closely related to the movement of the apple. In this scenario, the 1N force is being applied over a distance of 1 meter, resulting in 1 joule of work being done. This work is what allows the apple to overcome the force of gravity and reach a height of 1 meter.

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