Newtons 3rd Law Review worksheet - Free Printable
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Step-by-step solution for: Newtons 3rd Law Review worksheet
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Show Answer Key & Explanations
Step-by-step solution for: Newtons 3rd Law Review worksheet
Let's go through each scenario and identify the action and reaction forces based on Newton’s 3rd Law of Motion, which states:
> *"For every action, there is an equal and opposite reaction."*
This means that whenever one object exerts a force on another, the second object exerts a force of equal magnitude but in the opposite direction on the first.
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- Action: The cannon exerts a forward force on the cannonball.
- Reaction: The cannonball exerts an equal and opposite backward force on the cannon (causing recoil).
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- Action: The rocket engines push exhaust gases downward.
- Reaction: The exhaust gases push the rocket upward with equal force.
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- Action: Air inside the balloon pushes downward as it escapes.
- Reaction: The balloon pushes upward due to the escaping air (this causes it to rise).
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- Action: The hammer exerts a downward force on the nail.
- Reaction: The nail exerts an equal and opposite upward force on the hammer.
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- Action: The first domino exerts a force on the second domino, pushing it over.
- Reaction: The second domino exerts an equal and opposite force back on the first (though this doesn’t stop the first from falling).
> Note: In this case, the reaction force is internal to the system, and the chain reaction continues due to momentum.
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- Action: The hand exerts a downward force on the spring.
- Reaction: The spring exerts an equal and opposite upward force on the hand.
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- Action: The cue ball exerts a force on the next ball (e.g., the white ball).
- Reaction: The next ball exerts an equal and opposite force back on the cue ball (causing it to slow or change direction).
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- The action is: RJ exerts a 50 N force on the baseball.
- The reaction is: The baseball exerts a 50 N force back on RJ’s bat (and ultimately on RJ’s arm).
- To achieve more of a reaction, RJ would have to increase the force applied (e.g., swing harder), because the reaction force is equal to the action force.
> Note: While both objects experience the same magnitude of force, the baseball accelerates more because it has less mass than RJ (and his bat). This is consistent with Newton’s 2nd Law: $ F = ma $ — for the same force, smaller mass → greater acceleration.
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| Scenario | Action | Reaction |
|--------|--------|----------|
| Cannon | Cannon pushes cannonball forward | Cannonball pushes cannon backward |
| Rocket | Rocket pushes exhaust downward | Exhaust pushes rocket upward |
| Balloon | Air pushes down | Balloon pushes up |
| Hammer & Nail | Hammer pushes nail down | Nail pushes hammer up |
| Dominoes | First domino pushes second | Second domino pushes back on first |
| Spring | Hand pushes spring down | Spring pushes hand up |
| Billiards | Cue ball pushes other ball | Other ball pushes back on cue ball |
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- Equal and opposite forces always occur in pairs.
- The effect (acceleration) depends on mass — lighter objects accelerate more.
- Force is mutual — both objects feel the same amount of force.
✔ So, even though the forces are equal, the baseball moves much faster than RJ because it has much less mass.
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Let me know if you'd like a diagram or further explanation!
> *"For every action, there is an equal and opposite reaction."*
This means that whenever one object exerts a force on another, the second object exerts a force of equal magnitude but in the opposite direction on the first.
---
1. Cannon firing a cannonball
- Action: The cannon exerts a forward force on the cannonball.
- Reaction: The cannonball exerts an equal and opposite backward force on the cannon (causing recoil).
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2. Rocket launch
- Action: The rocket engines push exhaust gases downward.
- Reaction: The exhaust gases push the rocket upward with equal force.
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3. Balloon releasing air
- Action: Air inside the balloon pushes downward as it escapes.
- Reaction: The balloon pushes upward due to the escaping air (this causes it to rise).
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4. Hammer hitting a nail
- Action: The hammer exerts a downward force on the nail.
- Reaction: The nail exerts an equal and opposite upward force on the hammer.
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5. Dominoes falling
- Action: The first domino exerts a force on the second domino, pushing it over.
- Reaction: The second domino exerts an equal and opposite force back on the first (though this doesn’t stop the first from falling).
> Note: In this case, the reaction force is internal to the system, and the chain reaction continues due to momentum.
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6. Hand pressing down on a spring
- Action: The hand exerts a downward force on the spring.
- Reaction: The spring exerts an equal and opposite upward force on the hand.
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7. Cue ball striking other balls in billiards
- Action: The cue ball exerts a force on the next ball (e.g., the white ball).
- Reaction: The next ball exerts an equal and opposite force back on the cue ball (causing it to slow or change direction).
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RJ Hits a Baseball with 50 N
- The action is: RJ exerts a 50 N force on the baseball.
- The reaction is: The baseball exerts a 50 N force back on RJ’s bat (and ultimately on RJ’s arm).
- To achieve more of a reaction, RJ would have to increase the force applied (e.g., swing harder), because the reaction force is equal to the action force.
> Note: While both objects experience the same magnitude of force, the baseball accelerates more because it has less mass than RJ (and his bat). This is consistent with Newton’s 2nd Law: $ F = ma $ — for the same force, smaller mass → greater acceleration.
---
Final Summary:
| Scenario | Action | Reaction |
|--------|--------|----------|
| Cannon | Cannon pushes cannonball forward | Cannonball pushes cannon backward |
| Rocket | Rocket pushes exhaust downward | Exhaust pushes rocket upward |
| Balloon | Air pushes down | Balloon pushes up |
| Hammer & Nail | Hammer pushes nail down | Nail pushes hammer up |
| Dominoes | First domino pushes second | Second domino pushes back on first |
| Spring | Hand pushes spring down | Spring pushes hand up |
| Billiards | Cue ball pushes other ball | Other ball pushes back on cue ball |
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Key Concept Recap:
- Equal and opposite forces always occur in pairs.
- The effect (acceleration) depends on mass — lighter objects accelerate more.
- Force is mutual — both objects feel the same amount of force.
✔ So, even though the forces are equal, the baseball moves much faster than RJ because it has much less mass.
---
Let me know if you'd like a diagram or further explanation!
Parent Tip: Review the logic above to help your child master the concept of action reaction worksheet.
