Newton's third law and energy transfer

In summary: It takes energy to move an object through a distance. And in the second question about punching the book, would the same outcome happen to any object punched repeteadly. Yes, any object that is punched repeatedly will absorb energy and potentially heat up. In summary, the conversation discusses the relationship between Newton's third law and energy transfer. It is clarified that Newton's third law is about force, not energy, and that applying a force does not necessarily require energy. The example of punching a book repeatedly is used to demonstrate the absorption of energy through deformation and heat. The concept of potential and kinetic energy is also discussed, with the conclusion that energy is lost and gained through different forms during movement and impact.
  • #1
Berney123
8
0
If Newtons third law says there is an equal and opposite reaction how can there be energy transfer.
For example if I push a box and give it 1000 joules of energy wouldn't it "give back" the energy. Also does an object have to be moved for it to gain energy, if I were to punch a book many times would it gain energy or is it just giving back the energy becausE of Newtons third law. And if I drop a ball from a height of 10 feet wouldn't it gain energy after it hits the ground because I am supplying it with potential energy than it is converted into kinetic as it falls once it hits the ground the energy is transferred into the ground and then back into the ball therefore giving the ball more energy than when it started. Please correct me if I am wrong
 
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  • #2
Recall the definition of work, which is force acting over a distance; the direction of the force matters. If I push a box 1m along the X axis, with a force of 1N, I have expended 1J of energy, because the displacement is in the direction of the force. The box on the other hand absorbed 1J or energy(or rather friction did), as the force it applied was opposite the displacement.
 
  • #3
Welcome to PF!
Berney123 said:
If Newtons third law says there is an equal and opposite reaction how can there be energy transfer.
For example if I push a box and give it 1000 joules of energy wouldn't it "give back" the energy.
Newton's 3rd law is about force not energy. If you apply a force to a box, it applies a force back at you.
Also does an object have to be moved for it to gain energy, if I were to punch a book many times would it gain energy or is it just giving back the energy becausE of Newtons third law.
There are different kinds of energy. If you punch a book a bunch of times and it doesn't move, it will absorb energy due to deformation and heat up.
And if I drop a ball from a height of 10 feet wouldn't it gain energy after it hits the ground...
It loses potential energy and gains kinetic energy until it hits the ground. Then it loses the (linear) kinetic energy too, converting it to heat and sound.
 
  • #4
In my first question you said that the box applies a force back to you, but doesn't it take energy to supply a force. And in the second question about punching the book, would the same outcome happen to any object punched repeteadly.
 
  • #5
Berney123 said:
In my first question you said that the box applies a force back to you, but doesn't it take energy to supply a force.
...
No. It does not take energy to apply a force.
 

1. What is Newton's Third Law?

Newton's Third Law of Motion states that for every action, there is an equal and opposite reaction. This means that whenever an object exerts a force on another object, the second object will exert an equal and opposite force back.

2. How does Newton's Third Law relate to energy transfer?

Newton's Third Law is closely related to the concept of energy transfer. When one object exerts a force on another object, energy is transferred from one object to the other. This can be seen in examples such as a ball hitting a wall, where the ball transfers its energy to the wall upon impact.

3. Can Newton's Third Law be applied to all types of energy?

Yes, Newton's Third Law can be applied to all types of energy, including kinetic, potential, thermal, and electromagnetic energy. This is because all types of energy involve some form of force or motion, which is governed by Newton's Third Law.

4. How does Newton's Third Law explain the motion of objects?

Newton's Third Law explains the motion of objects by stating that forces always occur in pairs. When an object exerts a force on another object, the second object will exert an equal and opposite force back. This results in a change in motion, as the forces act in opposite directions.

5. Are there any limitations to Newton's Third Law?

While Newton's Third Law is a fundamental principle in physics, it does have some limitations. It only applies to objects that are in direct contact with each other, and it does not take into account external forces such as air resistance or friction. Additionally, it does not explain the cause of the forces, only the relationship between them.

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