Mass Measuring Instruments | 9th Physics PTCB Complete Guide

Mass Measuring Instruments | 9th Physics PTCB Complete Guide

⚖️ Mass Measuring Instruments: Simple Guide 🌟 Introduction

Have you ever wondered how shopkeepers know how much rice 🍚 or sugar you're buying? Or how doctors measure your weight at the hospital? 🏥

Today we'll learn about measuring mass! 📊

🤔 Wait! Mass vs Weight - Are They Same? Most People Think:

"Mass and weight are the same!" ❌

But in Physics:

They are DIFFERENT! ✅

┌─────────────────────────────────────┐ │ MASS vs WEIGHT │ ├─────────────────────────────────────┤ │ │ │ MASS ⚖️ │ │ • Amount of matter in object │ │ • NEVER changes │ │ • Measured in: kg, g │ │ • Same on Earth & Moon! 🌍🌙 │ │ │ │ WEIGHT 🏋️ │ │ • Force pulling you down │ │ • CAN change │ │ • Measured in: Newton (N) │ │ • Different on Earth & Moon! 🌍🌙 │ │ │ └─────────────────────────────────────┘ Easy Example: You on Earth 🌍: Mass = 50 kg ✅ Weight = 490 N ✅

You on Moon 🌙: Mass = 50 kg ✅ (SAME!) Weight = 80 N (LESS! Moon pulls less)

Remember: Your mass stays same everywhere, but weight changes! 🎯

🏋️ Two Ways to Measure ┌──────────────────────────────────┐ │ To Measure WEIGHT 🏋️ │ │ Use: Spring Balance │ │ (pulls down, uses spring) │ │ │ │ To Measure MASS ⚖️ │ │ Use: Physical Balance │ │ (compares with known mass) │ └──────────────────────────────────┘ ⚖️ The Physical Balance 🎯 What is it?

A Physical Balance is a tool that compares mass of an object with known standard masses!

┌─────────────┐ │ Pointer │ │ ↕ │ ├─────┴──────┤ │ Beam │ ├─────┬──────┤ ╱ │ ╲ ╱ │ ╲ ╱ │ ╲ ┌─┐ │ ┌─┐ │?│ Balance │5g│ └─┘ └─┘ Left Pan Right Pan (Object) (Weights) 🎯 How Does It Work?

Based on LEVER principle! 🎪

Think of a see-saw:

Person A Person B 👦 ───────⚖───────── 👧 Heavy Light (going down) (going up)

Person C Person D 👦 ───────⚖───────── 👦 Same Same (BALANCED! ⚖️)

Same in Physical Balance:

• Left side = Unknown object
• Right side = Known weights
• When balanced = Both have same mass! ✅

🛠️ Parts of Physical Balance (Simple!) ┌────────────────────────────────────┐ │ │ │ Pointer ↕ │ │ │ │ │ ═════════════ Beam │ │ ║ ║ │ │ ║ ║ │ │ ┌───┐ ┌───┐ │ │ │ ? │ │5g │ Pans │ │ └───┘ └───┘ │ │ ║ ║ │ │ Stand Stand │ │ ║ ║ │ │ ═══════════════════ Base │ │ │ └────────────────────────────────────┘

1. Base 🏗️

• Bottom part (like floor)
• Must be level (flat)

2. Beam ━━━

• Long horizontal bar
• Holds both pans

3. Pointer ↕️

• Thin needle in middle
• Shows if balanced or not

4. Pans 🍽️

• Two dishes (left and right)
• Hold objects and weights

5. Stand/Pillar 🏛️

• Vertical support
• Holds everything up

📖 How to Use Physical Balance (Step by Step!) 🎯 Before Starting: ╔══════════════════════════════════╗ ║ STEP 1: Make Base Level ║ ╚══════════════════════════════════╝

┌─────────────────┐ │ Plumb Line │ ← Hanging string │ ║ │ with weight │ ║ │ │ ▼ │ │ • ← Mark │ │ │ │ ═══════ Base │ └─────────────────┘

Turn screws until line is exactly above mark! ✅ ╔══════════════════════════════════╗ ║ STEP 2: Check If Beam is Level ║ ╚══════════════════════════════════╝

Pointer should be at ZERO:

-2 -1 0 +1 +2 ↑ Pointer here ✅

If not at zero: Turn balancing screws on beam! 🎯 Now Measure: ╔══════════════════════════════════╗ ║ STEP 3: Place Object ║ ╚══════════════════════════════════╝

┌────┐ ┌────┐ │ 🍎 │ │ │ └────┘ └────┘ Left Pan Right Pan (Object) (Empty) ╔══════════════════════════════════╗ ║ STEP 4: Add Known Weights ║ ╚══════════════════════════════════╝

┌────┐ ┌────┐ │ 🍎 │ │ 5g │ ← Add weights └────┘ │10g │ from box │20g │ (use forceps!) └────┘

Use forceps 🥢 (not fingers!) Don't touch weights directly! ╔══════════════════════════════════╗ ║ STEP 5: Check Pointer ║ ╚══════════════════════════════════╝

Too much weight on right: -2 -1 0 +1 +2 ↑ (Remove some weight)

Too much weight on left: -2 -1 0 +1 +2 ↑ (Add more weight)

Perfect balance: -2 -1 0 +1 +2 ↑ (BALANCED! ✅) ╔══════════════════════════════════╗ ║ STEP 6: Add Up All Weights ║ ╚══════════════════════════════════╝

Right Pan has: - 50g weight ✅ - 20g weight ✅ - 10g weight ✅ - 5g weight ✅ ─────────────── Total = 85g

So apple 🍎 = 85g ✅ 📦 Weight Box (What's Inside?) ┌─────────────────────────────────┐ │ WEIGHT BOX 📦 │ ├─────────────────────────────────┤ │ │ │ [100g] [50g] [20g] [10g] │ │ │ │ [5g] [2g] [1g] [500mg] │ │ │ │ [200mg] [100mg] [50mg] │ │ │ │ 🥢 Forceps │ │ │ └─────────────────────────────────┘

Different weights available:

• Big weights: 100g, 50g, 20g, 10g
• Small weights: 5g, 2g, 1g
• Very small: 500mg, 200mg, 100mg

Note: 1000 mg = 1 g

🎯 Example: Weighing a Mango 🥭 ╔══════════════════════════════════╗ ║ Weighing a Mango 🥭 ║ ╚══════════════════════════════════╝

STEP 1: Clean both pans ✅ STEP 2: Check level ✅ STEP 3: Place mango on left pan

┌─────┐ ┌─────┐ │ 🥭 │ │ │ └─────┘ └─────┘ Tilted! Going up! (Heavy) (Light)

STEP 4: Try 100g weight

┌─────┐ ┌─────┐ │ 🥭 │ │100g │ └─────┘ └─────┘ Still Still going down going up (Need more!) (Add more!)

STEP 5: Try 100g + 50g = 150g

┌─────┐ ┌─────┐ │ 🥭 │ │100g │ └─────┘ │ 50g │ └─────┘ Going up! Too much! (Less weight) (Remove some)

STEP 6: Try 100g + 20g + 10g = 130g

┌─────┐ ┌─────┐ │ 🥭 │ │100g │ └─────┘ │ 20g │ Balanced │ 10g │ ⚖️ └─────┘

STEP 7: Check pointer = at ZERO ✅

Answer: Mango = 130g ✅ ⚠️ Important Safety Rules! ┌────────────────────────────────┐ │ DO's ✅ │ ├────────────────────────────────┤ │ ✅ Clean pans before use │ │ ✅ Use forceps for weights │ │ ✅ Check level first │ │ ✅ Be gentle with balance │ │ ✅ Keep weights in box │ └────────────────────────────────┘

┌────────────────────────────────┐ │ DON'Ts ❌ │ ├────────────────────────────────┤ │ ❌ Touch weights with fingers │ │ ❌ Shake the balance │ │ ❌ Put hot objects on pans │ │ ❌ Overload the pans │ │ ❌ Leave weights out │ └────────────────────────────────┘ 💡 Common Mistakes (Avoid These!) Mistake 1: Not Checking Level ❌ Balance tilted = Wrong reading!

Base not level ╱╲ ╱ ╲ ╱════╲ ← Tilted!

Fix: Use levelling screws! ✅

Mistake 2: Touching Weights with Fingers ❌ Your fingers have: - Oil 🛢️ - Dirt 🦠 - Sweat 💧

This makes weights dirty and inaccurate!

Fix: Always use forceps! 🥢✅

Mistake 3: Not Checking Zero First ❌ Pointer not at zero BEFORE starting = Wrong measurement!

Fix: Check pointer is at 0 first! ✅

🌟 Real Example 1: Science Lab 🔬

Task: Find mass of a stone 🪨

┌──────────────────────────────────┐ │ Student's Notebook Entry 📓 │ ├──────────────────────────────────┤ │ │ │ Object: Small stone 🪨 │ │ Date: Today │ │ │ │ Steps: │ │ 1. Checked balance level ✅ │ │ 2. Cleaned pans ✅ │ │ 3. Put stone on left pan ✅ │ │ 4. Added weights: │ │ - First tried: 50g │ │ (Too much!) │ │ - Then tried: 20g + 10g │ │ (Too little!) │ │ - Finally: 20g + 10g + 5g │ │ (Perfect! ⚖️) │ │ │ │ 5. Pointer at zero ✅ │ │ │ │ Result: Stone mass = 35g ✅ │ │ │ └──────────────────────────────────┘ 🌟 Real Example 2: Market Scene 🏪

Imagine: Uncle at fruit shop weighing oranges 🍊

╔════════════════════════════════╗ ║ At the Fruit Shop 🏪 ║ ╚════════════════════════════════╝

Customer: "I want 1 kg oranges please!"

Uncle: "Sure! Let me weigh..."

┌─────────┐ ┌─────────┐ │ 🍊🍊🍊 │ │ 500g │ │ 🍊🍊🍊 │ │ 500g │ │ 🍊 │ │ │ └─────────┘ └─────────┘ 7 oranges 1000g weights (1 kg)

Balance tilted slightly...

Uncle adds one more: 🍊

┌─────────┐ ┌─────────┐ │ 🍊🍊🍊 │ │ 500g │ │ 🍊🍊🍊 │ │ 500g │ │ 🍊🍊 │ │ │ └─────────┘ └─────────┘ 8 oranges Balanced! ⚖️

Customer gets exactly 1 kg! ✅ 🎯 Quick Summary ┌────────────────────────────────┐ │ Physical Balance Summary │ ├────────────────────────────────┤ │ │ │ What: Measures MASS ⚖️ │ │ │ │ How: Compares with known │ │ standard weights │ │ │ │ Based on: Lever principle 🎪 │ │ │ │ Used in: Labs, shops, markets │ │ │ │ Important: Use forceps! 🥢 │ │ Check level first! │ │ │ └────────────────────────────────┘ 🧠 Remember Forever! ┌─────────────────────────────────┐ │ The 6 Golden Steps ✨ │ ├─────────────────────────────────┤ │ │ │ 1️⃣ Level the base │ │ 2️⃣ Check pointer at zero │ │ 3️⃣ Place object (left pan) │ │ 4️⃣ Add weights (right pan) │ │ 5️⃣ Adjust until balanced │ │ 6️⃣ Add up all weights = Answer │ │ │ └─────────────────────────────────┘

Memory Trick: "L-C-P-A-A-A"

• Level
• Check
• Place
• Add
• Adjust
• Answer

🎮 Quick Quiz!

Q1: Mass or Weight - which stays same on Moon?

• Answer: Mass! ⚖️ (Weight changes)

Q2: Which pan for unknown object?

• Answer: Left pan!

Q3: Should you touch weights with fingers?

• Answer: NO! ❌ Use forceps 🥢

Q4: What does pointer at zero mean?

• Answer: Balanced! Both sides equal! ⚖️✅

✨ Final Tips 🎯 Always be GENTLE 👀 Always CHECK zero first 🥢 Always use FORCEPS ⚖️ Always wait for BALANCE 📝 Always RECORD properly

You're now a weighing expert! 🏆⚖️

Remember: In science, we measure MASS, not weight! 💪✨