Action and reaction are equal and opposite,but why dont they cancell ?

The net contribution to linear momentum from a third law force pair is zero. However, when doing a force balance on an object, only the forces acting on the object are considered. This means that while the third law still applies, the forces do not cancel out on a single object because only one of the forces is taken into account. In summary, the forces of action and reaction are equal and opposite, but they do not cancel out on a single object due to the principles of force balance and the consideration of only forces acting on the object.
  • #1
tushar
1
0
Action and reaction are equal and opposite,but why don't they cancell ?...

Unlike other forces, like for example.. it a body is pressed from top and below with a same force.. the body stays there and its said that the forces cancell out.. why not here ?
 
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  • #2
They do cancel. The net contribution to linear momentum (totalled over both objects) from a third law force pair is zero.

They don't cancel on a single object because only one of the two forces acts on that object.
 
  • #3
The action is the force which you apply.

The reaction is the force which is applied on you.

So they cancel as a pair, but you must work out the dynamics by considering action-reaction separately ... like when a ball strikes a wall, or two balls collide.
 
  • #4
The third law says that the force you exert on an object is equal in magnitude and opposite In direction to the force that the object exerts on you. But, if you are doing a force balance on the object , you include only forces acting on the object, and not forces acting on you.

Chet
 
  • #5


I can explain this phenomenon using Newton's Third Law of Motion, which states that for every action, there is an equal and opposite reaction. This means that when a force is applied to an object, the object will exert an equal force in the opposite direction. However, it is important to understand that these forces act on different objects and therefore cannot cancel each other out.

In the example you provided, if an object is pressed from the top and bottom with equal forces, the object will not move because the forces are acting on the same object in opposite directions. The forces are balanced, resulting in no net force on the object, and therefore no movement.

However, in the case of action and reaction forces, they act on different objects. For instance, when you push on a wall, the wall exerts an equal and opposite force on you. These forces cannot cancel each other out because they are acting on different objects. Your force is acting on the wall, while the wall's force is acting on you. These forces are balanced, but they are not cancelling each other out.

In summary, action and reaction forces cannot cancel each other out because they act on different objects. It is the net force on an object that determines its motion, and in the case of action and reaction forces, the net force is zero.
 

1. How is it possible for action and reaction to be equal and opposite, but not cancel out?

According to Newton's third law of motion, for every action, there is an equal and opposite reaction. This means that when one object exerts a force on another object, the second object will exert an equal and opposite force back. However, these forces do not cancel out because they act on different objects and in opposite directions. The forces may have equal magnitudes, but they are still acting on different objects, resulting in a net force on each object.

2. Why is it important to understand the concept of equal and opposite forces?

Understanding the concept of equal and opposite forces is important because it helps us to predict and explain the motion of objects. It allows us to determine the direction and magnitude of forces acting on objects, which can help us to design and improve technologies such as vehicles and buildings. Additionally, understanding equal and opposite forces is crucial for understanding how the universe works and how objects interact with each other.

3. Can action and reaction forces be of different types?

Yes, action and reaction forces can be of different types. For example, if you push on a wall, the action force is a contact force (your hand pushing on the wall), but the reaction force is a normal force (the wall pushing back on your hand). Similarly, if a rocket engine produces a thrust force to propel the rocket forward, the reaction force is the exhaust gases pushing the rocket in the opposite direction.

4. What happens when the forces in an action-reaction pair are not equal?

If the forces in an action-reaction pair are not equal, the objects involved will experience an acceleration in the direction of the net force. This is because the net force is the sum of all the forces acting on an object, and any unbalanced force will result in a change in the object's motion. This is why it is important for forces to be balanced for an object to remain in a state of constant motion.

5. Are there any exceptions to Newton's third law of motion?

While Newton's third law of motion holds true in most situations, there are some exceptions. For example, in some cases, the surface on which an object is moving may deform due to the force applied, resulting in a slightly different reaction force. Additionally, in some situations, external forces such as friction or air resistance may affect the forces acting on an object, making them unequal. However, these exceptions do not invalidate the overall concept of equal and opposite forces.

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