2
Question Question 2
In the following example, try to identify the number of times the velocity of the ball changes:
'A football player kicks a football to another player of his team who kicks the football towards the goal. The goalkeeper of the opposite team collects the football and kicks it towards a player of his own team'.
Also identify the agent supplying the force in each case.
The velocity of the ball changes :
- When the football player kicks a football to another player,
- When that player kicks the football towards the goal.
- When the goalkeeper stops the football.
- When the goalkeeper kicks the football towards his team player.
Hence, the velocity of the football changes four times.
Agent supplying the force:
(a) The First case is the First player
(b) The Second case is the Second player
(c) The Third case is Goalkeeper
(d) The Fourth case is Goalkeeper
BRIGHT TUTORIALS
BRIGHT TUTORIALS
CBSE Class IX | Academic Year 2026-2027
9403781999
Excellence in Education
Science | Chapter 8: Force and Laws of MotionWeb Content — Quick Reference
Chapter 8: Force and Laws of Motion — Quick Reference
Quick Revision Points
- Balanced forces: net force = 0, no acceleration. Unbalanced: net force ≠ 0, causes acceleration
- First Law (Inertia): object stays at rest/uniform motion unless external force acts
- Momentum p = mv (kg·m/s); Second Law: F = ma = Δp/Δt
- 1 N = force giving 1 kg an acceleration of 1 m/s²
- Third Law: every action has equal and opposite reaction (on different bodies)
- Conservation of momentum: m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂ (no external force)
Exam Tips for Chapter 8
- Read the detailed chapter notes for complete coverage of all NCERT topics.
- Practice all NCERT in-text and back exercise questions — they are frequently asked in exams.
- Focus on comparison tables, diagrams, and definitions — these are high-scoring areas.
- For numericals (if applicable), practice at least 20 problems of varying difficulty.
- Refer to the practice question bank (200+ questions) for thorough preparation.
Related Resources
- Detailed Notes: ch08-force-and-laws-of-motion.html
- Practice Questions: 100+ questions with answers in 05-practice-questions/
- Chapter Test: 30-mark test paper in 06-tests/chapter-tests-30marks/
- Formula Sheet: Complete formula reference in 03-teacher-aid/formula-sheet.html
BRIGHT TUTORIALS
BRIGHT TUTORIALS
CBSE Class IX | Academic Year 2026-2027
9403781999
Excellence in Education
Science | Chapter 7: MotionWeb Content — Quick Reference
Chapter 7: Motion — Quick Reference
Quick Revision Points
- Distance (scalar, total path) vs Displacement (vector, shortest path)
- Speed = distance/time (scalar); Velocity = displacement/time (vector)
- Acceleration a = (v−u)/t; unit: m/s²
- Equations: v = u + at; s = ut + ½at²; v² = u² + 2as
- d-t graph slope = speed; v-t graph slope = acceleration; area under v-t = distance
- 1 km/h = 5/18 m/s; Free fall: u = 0, a = g = 9.8 m/s²
- Uniform circular motion: constant speed, changing velocity (direction changes)
Exam Tips for Chapter 7
- Read the detailed chapter notes for complete coverage of all NCERT topics.
- Practice all NCERT in-text and back exercise questions — they are frequently asked in exams.
- Focus on comparison tables, diagrams, and definitions — these are high-scoring areas.
- For numericals (if applicable), practice at least 20 problems of varying difficulty.
- Refer to the practice question bank (200+ questions) for thorough preparation.
Related Resources
- Detailed Notes: ch07-motion.html
- Practice Questions: 100+ questions with answers in 05-practice-questions/
- Chapter Test: 30-mark test paper in 06-tests/chapter-tests-30marks/
- Formula Sheet: Complete formula reference in 03-teacher-aid/formula-sheet.html