Identifying Action Reaction Forces: A Newton's Third Law Analysis

In summary, there are five pairs of action reaction forces in the given diagram: man and monkey, monkey and scale, scale and tree, man and rope, and monkey and rope. However, it is important to note that indirect forces, such as between the man and tree, do not count in Newton's third law. Only forces between objects in direct contact should be included.
  • #1
storygeek
7
0

Homework Statement


"Identify at least five pairs of action reaction forces in the following diagram"
u2l4a13.gif

Source: http://www.physicsclassroom.com/Class/newtlaws/U2L4b.html problem 2

Homework Equations


Newton's third law


The Attempt at a Solution


1) Man and monkey
2)monkey and scale
3)scale and tree
4)man and tree
5) monkey and tree
 
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  • #2
You would be better off sticking to things that are in actual contact and thus can push/pull against each other. For example, the man is touching the rope, so man and rope can exert forces on each other. But the man is not directly touching the tree, so man and tree do not directly exert forces on each other. (Note: A long range force, like gravity, does not require direct contact.)
 
  • #3
The best way to deal with things is to draw "bags" around things and see how the forces are acting on that single thing.

* Note *
You might want to think about tension =).
 
  • #4
Are my attempts to the solutions valid? Man exerts force on Monkey and vice versa. Do indirect forces count in Newton's third law? Like the one between the tree and man.
 
  • #5
storygeek said:
Are my attempts to the solutions valid? Man exerts force on Monkey and vice versa. Do indirect forces count in Newton's third law? Like the one between the tree and man.
Strictly speaking: No. Only include forces between objects that are in direct contact. (We ignore the teeny tiny gravitational force between man and tree!) The man doesn't really pull on the tree; he pulls on the rope! Redo your answers with this in mind and you'll have a deeper (and more correct) understanding of forces and Newton's 3rd law.
 

What is Newton's third law?

Newton's third law states that for every action, there is an equal and opposite reaction. This means that when an object exerts a force on another object, the second object will exert an equal and opposite force back.

What is an example of Newton's third law in action?

An example of Newton's third law is when you push against a wall. Your hand exerts a force on the wall, and the wall exerts an equal and opposite force back on your hand. This is why you can't push a wall over, because the wall is pushing back with the same force.

Are there any exceptions to Newton's third law?

No, there are no exceptions to Newton's third law. It applies to all interactions between objects, whether they are in motion or at rest.

How does Newton's third law relate to motion?

Newton's third law is related to motion because it explains how forces cause objects to move. When one object exerts a force on another, the second object will experience an equal and opposite force, causing it to accelerate in the opposite direction.

What is the significance of Newton's third law in science and everyday life?

Newton's third law is significant in science because it helps us understand the relationship between forces and motion. It also has practical applications in everyday life, such as in sports (e.g. hitting a baseball) and transportation (e.g. how rockets work).

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