Gravitation – Complete Intermediate Notes
Stage 1 • Page 4 • Mass, Weight & Weightlessness
1. Mass
Mass is the quantity of matter contained in a body.
- Scalar quantity
- Independent of location
- Remains constant everywhere
- SI unit: kilogram (kg)
Key Idea:
Mass measures inertia, not gravitational pull.
2. Weight
Weight is the gravitational force acting on a body due to Earth.
W = mg
- Vector quantity
- Acts vertically downward
- Depends on value of g
- SI unit: newton (N)
Exam Tip:
Weight changes with height, depth, latitude — mass never changes.
3. Difference Between Mass and Weight
| Mass | Weight |
|---|---|
| Constant | Variable |
| Scalar | Vector |
| kg | N |
4. Weightlessness
A body is said to be in a state of weightlessness when its apparent weight becomes zero.
This happens when:
- Body is in free fall
- Lift is falling freely
- Satellite is revolving around Earth
Important:
Weightlessness does NOT mean absence of gravity.
5. Apparent Weight
Apparent weight is the normal reaction exerted by the support on a body.
Depending on motion of lift:
- Lift at rest / uniform speed: Apparent weight = mg
- Lift accelerating upward: Apparent weight = m(g + a)
- Lift accelerating downward: Apparent weight = m(g − a)
- Free fall: Apparent weight = 0
IIT Favourite:
Lift problems are commonly mixed with Newton’s laws.
6. Apparent Weight on Other Planets
Weight of a body on another planet depends on its gravitational acceleration.
Wplanet = m gplanet
- Mass remains same
- Weight changes
- g depends on planet’s mass and radius
7. Common Mistakes to Avoid
- Confusing weightlessness with zero gravity
- Using mg during free fall
- Forgetting acceleration sign in lift problems
- Assuming mass changes on other planets
Stage 1 • Page 4 Completed Successfully ✅
📚 IIT JEE PHYSICS – COMPLETE MASTER LIBRARY
Concepts • Problems • Tough Questions • Exam Mastery • Topper Thinking
🌍 GRAVITATION – IIT JEE EXAM MASTERY (FULL SERIES)
Concept → Board → IIT → Tough → Mastery
- Gravitation – Part 1
- Gravitation – Part 2
- Gravitation – Part 3
- Gravitation – Part 4
- Gravitation – Part 5
- Gravitation – Part 6
- Gravitation – Part 7
- Gravitation – Part 8
- Gravitation – Part 9
- Gravitation – Part 10
- Gravitation – Part 11
- Gravitation – Part 12
- Gravitation – Part 13
- Gravitation – Part 14
- Gravitation – Part 15
- Gravitation – Part 16
- Gravitation – Part 17
- Gravitation – Part 18
- Gravitation – Part 19
- Gravitation – Part 20
- Gravitation – Part 21
- Gravitation – Part 22
- Gravitation – Part 23
- Gravitation – Part 24
- Gravitation – Part 25
- Gravitation – Part 26
- Gravitation – Part 27
- Gravitation – Part 28
- Gravitation – Part 29
- Gravitation – Part 30
- Gravitation – Part 31
- Gravitation – Part 32
- Gravitation – Part 34
- Gravitation – Part 35
- Gravitation – Part 36
- Gravitation – Part 37
- Gravitation – Part 38
- Gravitation – Part 39
- Gravitation – Part 40
- Gravitation – Part 41
- Gravitation – Part 42
📘 OTHER PHYSICS LIBRARIES
- Momentum & Collisions – Complete Library
- Centre of Mass & System of Particles – Complete Library
- Work, Energy & Power – Complete Library
🧠 THINKING & FOUNDATION
🌐 MASTER HUBS
📲 STUDENT COMMUNITY
✅ IIT JEE PHYSICS LIBRARY – COMPLETE | STRUCTURED | EXAM-ORIENTED
No comments:
Post a Comment