15 Questions
What is the fundamental principle behind Newton's third law of motion?
For every action, there is an equal and opposite reaction
What is another name for Newton's third law of motion?
The action-reaction law
What is the relationship between the action force and reaction force in Newton's third law of motion?
The action force is always equal to the reaction force
Why do the action and reaction forces not cancel each other out?
Because the forces act on different objects
What would happen if the equal and opposite forces were exerted on the same object?
The forces would cancel each other out
What is the example of Newton's third law of motion mentioned in the passage?
A rowboat moving through the water
What is the role of the person in the rowboat in the example of Newton's third law of motion?
The person exerts a force only on the water
What is necessary for the cancellation of motion to occur?
The action force and reaction force are acting on the same object.
What happens when the person in the rowboat exerts force on the water?
The person and the boat move forward due to the reaction force.
Why does the rowboat move forward in the water but not on land?
The water has more mass than the cup of water on the land.
How do rocket ships and fighter jets operate?
By using both action and reaction forces.
What is the result of the action force of the engine and tires spinning on the ground?
The car moves forward.
What is an example of the application of Newton's third law of motion besides rocket ships?
A water mill generating electricity.
What is the purpose of the induction generator in a water mill?
To convert motion into electricity.
Why does a person move forward when walking?
Because the person's muscles create an action force that the feet exert on the ground, and the reaction force of the ground is exerted on the person's body.
Study Notes
Newton's Third Law of Motion
- States that for every action, there is an equal and opposite reaction
- When one object exerts a force on a second object, the second object exerts a force on the first that is equal but opposite in direction
Examples of Newton's Third Law
- Rowboat: person exerts a force on the water using a paddle, and the water exerts a force on the rowboat and person
- Rocket ships: combustion of fuel creates an action force on the expanding gases, and the expanding gases exert an equal reaction force on the rocket ship
- Fighter jets: engine exerts an action force on the air, and the air exerts an equal reaction force on the fighter jet
- Cars: engine and tires exert an action force on the ground, and the ground exerts an equal reaction force on the car
- Bicycles: pedaling exerts an action force on the ground, and the ground exerts an equal reaction force on the bicycle
- Walking: muscles exert an action force on the ground, and the ground exerts an equal reaction force on the body
Key Points
- Action and reaction forces act on different objects
- Forces do not cancel each other out because they act on different objects
- If action and reaction forces act on the same object, they will cancel each other out
Applications of Newton's Third Law
- Rocket propulsion
- Fighter jet propulsion
- Conversion of motion into electricity (e.g. water mills)
- Everyday activities like walking, biking, and driving
Understand Newton's third law of motion, also known as the action-reaction law, which states that every action has an equal and opposite reaction.
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