SEBA Class 9 Science Important Chapter 9 Force and Laws of Motion Solutions English Medium As Per SEBA New Syllabus to each chapter is provided in the list so that you can easily browse through different chapters SEBA Class 9 General Science Additional Solutions and select need one. NCERT Important Solutions For Class 9 General Science Download PDF. Important Notes for Class 9 Science.
SEBA Class 9 Science Important Chapter 9 Force and Laws of Motion
Also, you can read the NCERT book online in these sections Solutions by Expert Teachers as per Central Board of Secondary Education (CBSE) Book guidelines. Assam SEBA Board Class 9 Science Additional Question Answer are part of All Subject Solutions. Here we have given CBSE Class 9 Science Important Notes for All Chapters, You can practice these here.
Force and Laws of Motion
Chapter: 9
| IMPORTANT QUESTION ANSWER |
Answer the Following Question:
1. What is the SI unit of force?
Ans: Newton (N).
2. What is the direction of acceleration when an unbalanced force acts on an object?
Ans: In the direction of the applied force.
3. What is the unit of momentum in SI?
Ans: kg·m/s.
4. What happens to the motion of an object if the net external force on it is zero?
Ans: It remains at rest or moves with uniform velocity.
5. What is the reaction when you walk forward by pushing the ground backward?
Ans: The ground pushes you forward (reaction force).
6. Which law explains rocket propulsion?
Ans: Newton’s Third Law of Motion.
7. Define force. What are its effects on a body?
Ans: Force is a push or pull acting on an object. It can change the object’s speed, direction of motion, shape, or state (from rest to motion or vice versa).
8. State Newton’s First Law of Motion with an example.
Ans: Newton’s First Law states that an object remains at rest or in uniform motion in a straight line unless acted upon by an unbalanced external force.
Example: A book on a table stays at rest unless someone pushes it.
9. Define momentum. State its SI unit.
Ans: Momentum is the product of mass and velocity of an object.
p = m × v
SI unit: kg·m/s.
10. State and explain Newton’s Second Law of Motion.
Ans: It states that the rate of change of momentum is directly proportional to the applied force and takes place in the direction of force.
Formula: F = ma
11. A force of 10 N is applied on a body of mass 5 kg. What is the acceleration?
Ans: F = ma → F/m = 10/5 = 2 m/s2
12. Why do passengers fall forward when a bus suddenly stops?
Ans: Due to inertia of motion, the lower body comes to rest with the bus, but the upper body tends to remain in motion, causing passengers to fall forward.
13. Define Newton’s Third Law with an example.
Ans: For every action, there is an equal and opposite reaction.
Example: Recoil of a gun—bullet moves forward, and gun moves backward.
14. State the law of conservation of momentum.
Ans: Total momentum of a system remains conserved if no external force acts on it.
Formula: m1u1 + m2u2 = m1v1 + m2v2m
15. Explain the term ‘reaction force’ with an example.
Ans: When you apply a force (action) on a surface, the surface applies an equal and opposite force (reaction).
Example: Walking – feet push ground backward, ground pushes forward.
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