Newton's Second Law: Mass, Force, and Motion — Slingshot Experiment Worksheet

You’re working on Newton’s Second Law: Mass, Force, and Motion, specifically Part I: Slingshot Experiment. Let’s break down each question and explain the science behind the answers using Newton’s Second Law (F = ma) — which says that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass.

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Question 1:

> Marissa puts Marble A in the pocket of the slingshot. She pulls the pocket back 12 inches and then releases it. What happens to the marble? Explain why.

✔ Answer:
Marble A will be launched forward and travel a certain distance. When Marissa pulls the slingshot back 12 inches, she stores elastic potential energy in the rubber bands. When released, that energy is converted into kinetic energy, accelerating the marble forward.

Why?
According to Newton’s Second Law, F = ma, the force from the slingshot causes the marble (with mass *m*) to accelerate (*a*). Since Marble A has a typical mass, it will accelerate at a moderate rate and travel a moderate distance.

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Question 2:

> Marissa now pulls the pocket back 12 inches and launches Marble B in the same direction and at the same angle as before. Will the marble travel farther than before? Explain why or why not.

✔ Answer:
No, Marble B will NOT travel farther than Marble A — it will travel a SHORTER distance.

Why?
Even though the slingshot is pulled back the same distance (so the *force applied is the same*), Marble B has more mass than Marble A.

Recall F = ma → a = F/m.
If force (F) is constant but mass (m) increases, then acceleration (a) decreases.

So, Marble B experiences less acceleration than Marble A when launched with the same force. That means it leaves the slingshot with a lower initial velocity, and therefore travels a shorter distance.

📌 Key Concept: For the same force, a heavier object accelerates less → lower speed → shorter range.

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Question 3:

> Next, Marissa puts Marble B in the slingshot. She pulls the pocket back 18 inches, keeping the same direction and angle as before, and releases it. Will Marble B travel farther than Marble A did in the previous launch? Explain why or why not.

✔ Answer:
Yes, Marble B will likely travel farther than Marble A did in the first launch.

Why?
This time, Marissa pulls the slingshot back farther (18 inches instead of 12). This means she applies more force to Marble B — because stretching the rubber band more increases the elastic force (like a spring: F ∝ stretch).

Even though Marble B has more mass, the increased force can compensate for the increased mass.

Let’s think about it:

- Marble A: small mass, medium force → medium acceleration → medium distance.
- Marble B: larger mass, larger force → possibly similar or even greater acceleration → possibly greater distance.

In fact, since force increased by 50% (from 12" to 18"), and mass only increased “a bit” (as stated: “a bit bigger”), the net acceleration may be higher for Marble B this time.

Also, in real-world projectile motion, initial velocity determines how far something goes (if angle and height are the same). If the increased force gives Marble B a higher launch speed than Marble A had, then yes — it will go farther.

📌 Key Concept: Increasing the force (by pulling farther) can overcome the effect of increased mass, leading to greater acceleration and distance.

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## ✔ Summary of Answers:

| Question | Answer | Reason |
|----------|--------|--------|
| 1 | Marble A launches forward and travels a moderate distance. | Force from slingshot accelerates it based on its mass (F=ma). |
| 2 | No, Marble B travels shorter than Marble A. | Same force, but more mass → less acceleration → lower speed → shorter distance. |
| 3 | Yes, Marble B travels farther than Marble A did in Q1. | Greater force (pulled farther) compensates for higher mass → potentially higher acceleration/speed → longer distance. |

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## 🧠 Bonus Tip:
This experiment shows how force, mass, and acceleration are interconnected — exactly what Newton’s Second Law teaches! You can’t just say “heavier things don’t go as far” — you must consider how much force is applied too.

Great job exploring physics through hands-on experiments! 🚀

Let me know if you want help with Part II or any diagrams!