A thin flat circular disc of radius 4.5 cm is placed gently over the surface of water. If surface te

A thin flat circular disc of radius 4.5 cm is placed gently over the surface of water. If surface tension of water is 0.07 Nm-1, then the excess force required to take it away from the surface is :
(1) 19.8 mN
(2) 198 N
(3) 1.98 mN
(4) 99 N

*Title:* Surface Tension and Excess Force Calculation | Physics for IIT JEE & NEET 2025

*Description:*

Welcome to our channel! In today’s video, we dive into the fascinating topic of *surface tension* and explore how to calculate the *excess force* required to remove a thin disc from the surface of water. This concept is essential for *IIT JEE* and *NEET* aspirants, as surface tension plays a critical role in fluid mechanics.

🔍 *What You’ll Learn:*
1. **Understanding Surface Tension**:
- A clear explanation of what surface tension is, and why it occurs at the liquid's surface.
- How surface tension affects objects in contact with the liquid surface.

2. **Force Due to Surface Tension**:
- Explanation of how surface tension contributes to the force required to separate an object from a liquid surface.
- The formula to calculate this force: \( F = 2 \times \text{Surface Tension} \times \text{Circumference} \).
- Real-world applications of this concept in various fields such as biology, engineering, and everyday life.

3. **Circular Disc and Surface Tension**:
- How to calculate the *excess force* required to remove a thin flat circular disc from the surface of water.
- Step-by-step approach to understanding the relationship between the radius of the disc, surface tension of water, and the required force.

4. **Practical Examples and Exam-Relevant Problems**:
- Insight into how similar problems can appear in competitive exams like *IIT JEE* and **NEET**.
- Tips on solving surface tension-related questions quickly and effectively.

5. **Common Mistakes to Avoid**:
- Key pitfalls students face when dealing with surface tension problems, and how to avoid them in exams.

💡 **Why This Topic is Important for IIT JEE and NEET**:
- Surface tension is a crucial concept in fluid mechanics, frequently tested in both IIT JEE and NEET exams. Mastering this topic will help you solve many practical problems in physics.

📚 **Related Concepts**:
- **Fluid Mechanics and Buoyancy**: [Link to Video]
- **Viscosity and Fluid Flow**: [Link to Video]
- **Capillary Action and Applications**: [Link to Video]

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#IITJEE2025 #NEET2025 #SurfaceTension #FluidMechanics #ExcessForce #PhysicsConcepts #JEE2025 #NEET2025 #PhysicsPreparation

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This description covers the topic of surface tension and excess force, tailored to IIT JEE and NEET aspirants while maintaining the team-focused tone you prefer.
To find the excess force required to take the disc away from the surface of water, we can use the formula for the force due to surface tension:
Step-by-step Calculation:
1. **Circumference of the disc**:
\[
2. **Excess force required**:
The force is calculated by multiplying the surface tension and the circumference, then multiplying by 2 (since both the upper and lower surfaces of the disc are in contact with the water):

3. **Convert to milliNewtons**:

Thus, the excess force required is approximately **39.56 mN**.

Conclusion:
Based on the given options, the closest option seems to be missing. However, if there’s an error in the options provided, the correct value is approximately **39.56 mN**. Let me know if you'd like a related YouTube description!
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