Action-Reaction Forces (Simple Problems)

  • Thread starter rwishka
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So, for the first question, the action-reaction pair would be a, and the forces exerted by each object would be equal in magnitude and opposite in direction to each other. For the second question, the action-reaction pair would be c, and the forces exerted by each object would be equal in magnitude and opposite in direction to each other. For the third question, the player's shoes exert a force on the floor, and the floor exerts an equal and opposite force on the shoes, so the answer would be b. Does that make sense?In summary, the action-reaction pairs for the given scenarios are a, c, and b respectively, with the forces exerted by each object being equal in magnitude and opposite in
  • #1
rwishka
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Homework Statement



I promise - my last set of questions.

1. A hockey stick hits a puck on the ice. Identify an action-reaction pair, and compare the forces exerted by each object.

a. The stick exerts a force on the puck; the puck exerts a force on the stick.
b. The stick exerts a force on the puck; the puck exerts a force on the ice.
c. The puck exerts a force on the stick; the stick exerts a force on the ice.
d. The stick exerts a force on the ice; the ice exerts a force on the puck.

2. A leaf falls from a tree and lands on the sidewalk. Identify an action-reaction pair, and compare the forces exerted by each object.

a. The tree exerts a force on the leaf; the sidewalk exerts a force on the leaf.
b. The leaf exerts a force on the sidewalk; the sidewalk exerts a force on the leaf.
c. The leaf exerts a force on the tree; the sidewalk exerts a force on the leaf.
d. The leaf exerts a force on the sidewalk; the tree exerts a force on the leaf.

3. As a basketball player starts to jump for a rebound, the player begins to move upward faster and faster until his shoes leave the floor. During the time that the player is in contact with the floor, the force of the floor on the shoes is:

a. greater than the player's weight.
b. equal in magnitude and opposite in direction to the player's weight.
c. less than the player's weight.
d. zero

Homework Equations



None

The Attempt at a Solution



As you can see, I have trouble understanding these type of problems.

1. Would it be B, for isn't it like a chain reaction?
2. Would it be c, because the leaf will fall, and the sidewalk's force will make it stay for the time.
3. I think it would be either c or d, because if it was greater than the player's weight, he wouldn't jump, right?

I may be completely off, but I really need help with this! Please. :eek:
 
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  • #2
Does no one know how to do these? I really need to know how soon! Please kindly help me.
 
  • #3
rwishka said:

Homework Statement



I promise - my last set of questions.

1. A hockey stick hits a puck on the ice. Identify an action-reaction pair, and compare the forces exerted by each object.

a. The stick exerts a force on the puck; the puck exerts a force on the stick.
b. The stick exerts a force on the puck; the puck exerts a force on the ice.
c. The puck exerts a force on the stick; the stick exerts a force on the ice.
d. The stick exerts a force on the ice; the ice exerts a force on the puck.

2. A leaf falls from a tree and lands on the sidewalk. Identify an action-reaction pair, and compare the forces exerted by each object.

a. The tree exerts a force on the leaf; the sidewalk exerts a force on the leaf.
b. The leaf exerts a force on the sidewalk; the sidewalk exerts a force on the leaf.
c. The leaf exerts a force on the tree; the sidewalk exerts a force on the leaf.
d. The leaf exerts a force on the sidewalk; the tree exerts a force on the leaf.

3. As a basketball player starts to jump for a rebound, the player begins to move upward faster and faster until his shoes leave the floor. During the time that the player is in contact with the floor, the force of the floor on the shoes is:

a. greater than the player's weight.
b. equal in magnitude and opposite in direction to the player's weight.
c. less than the player's weight.
d. zero

Homework Equations



None

The Attempt at a Solution



As you can see, I have trouble understanding these type of problems.

1. Would it be B, for isn't it like a chain reaction?
2. Would it be c, because the leaf will fall, and the sidewalk's force will make it stay for the time.
3. I think it would be either c or d, because if it was greater than the player's weight, he wouldn't jump, right?

I may be completely off, but I really need help with this! Please. :eek:
You're way off. For action-reaction pairs, Newton's 3rd law states that if an object A exerts a force on object B, then object B must exert a force on object A, that is equal in magnitude, but opposite in direction. For your last question, if the jumper moves faster and faster during the time he is in contact with the floor, he must be accelearting during that period. What does Newton 2 tell you about or bodies that are accelerating??
 
  • #4
So would it be greater than the player's weight, as it is inversely proportional?? I think I have this all mixed up.
 
  • #5
rwishka said:
So would it be greater than the player's weight, as it is inversely proportional?? I think I have this all mixed up.
Well, it will be greater, on account of Newton 2: there must be a net force acting on the jumper in order for her to accelerate in the direction of the net force. Since her weight always acts down , the floor must push up with a force greater than her weight, in order for there to be a net force acting up to accelearte her off the floor.
 
  • #6
I see. Can you help me with the other ones please?
 
  • #7
rwishka said:
I see. Can you help me with the other ones please?
Gee, I thought i did. If a stick exerts a force on a puck, the puck exerts an equal force on the stick, in the opposite direction. These are force pairs per Newton 3. Sure there are forces of the ice on the puck, or the stick on the ice, but the problem is not asking about these. It asks for the action-reaction pairs to be chosen from the given choices.
 

What is an action-reaction force?

An action-reaction force is a pair of forces that occur simultaneously when two objects interact with each other. These forces are equal in magnitude but opposite in direction, and they are also known as Newton's Third Law of Motion.

Can you give an example of an action-reaction force?

An example of an action-reaction force is when a person pushes against a wall. The person exerts a force on the wall (action force), and the wall exerts an equal and opposite force on the person (reaction force). Another example is when a car accelerates forward, the tires push backward on the ground, and the ground pushes forward on the tires with an equal force.

How do you calculate the magnitude of an action-reaction force?

The magnitude of an action-reaction force can be calculated using Newton's Third Law, which states that the forces are equal in magnitude. This means that if the action force is 10 Newtons, the reaction force will also be 10 Newtons.

Do action-reaction forces always cancel each other out?

No, action-reaction forces do not cancel each other out because they act on different objects. However, they will cancel out if they act on the same object, but in opposite directions.

How do action-reaction forces affect the motion of an object?

Action-reaction forces do not affect the motion of an object. This is because the forces are acting on different objects and in opposite directions, causing a net force of zero. Therefore, the object will either remain at rest or continue moving at a constant velocity.

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