SEBA Class 9 Science Important Chapter 10 Gravitation

SEBA Class 9 Science Important Chapter 10 Gravitation 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 10 Gravitation

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.

Gravitation

Chapter: 10

IMPORTANT QUESTION ANSWER

Answer the Following Question:

1.  What is the value of the gravitational constant (G)?

Ans: G = 6.674 × 10⁻¹¹Nm²/kg²

2. Define thrust.

Ans: Thrust is a force applied perpendicularly to a surface.

3. What does Archimedes’ Principle state?

Ans: A body submerged in a fluid experiences an upward buoyant force equal to the weight of the fluid displaced.

4. What is the SI unit of pressure?

Ans: Pascal (Pa).

5. What is the effect of depth on pressure in liquids?

Ans: Pressure increases with depth in liquids.

6. State and explain Archimedes’ principle with an example.

Ans: Archimedes’ principle states that when a body is partially or fully immersed in a fluid, it experiences an upward force (buoyant force) equal to the weight of the fluid displaced.

Example: A ship floats on water because its design ensures it displaces water equal to its own weight.

7. State the Universal Law of Gravitation.

Ans: Every object in the universe attracts every other object with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.

8. Why does a sharp knife cut better than a blunt one?

Ans: A sharp knife has less surface area, hence exerts more pressure for the same thrust, making cutting easier.

9. Explain how to calculate the value of ‘g’ using Newton’s law.

Ans: Using formula:

g = GM/R²

Where,

G = 6.7 × 10⁻¹¹ N m²/kg²,

M = 6 × 10²⁴ kg (mass of Earth),

R = 6.4 × 10⁶ m (radius of Earth),

Putting values:

g ≈ 9.8 m/s²

10. Differentiate between mass and weight.

Ans: 

Mass	Weight
(i) Scalar quantity	(i) Vector quantity
(ii) Constant everywhere	(ii) Changes with gravity
(iii) SI unit: kilogram (kg)	(iii) SI unit: newton (N)
(iv) Measured using beam balance	(iv) Measured using spring balance

11. Why do all objects fall at the same rate towards the Earth, despite having different masses?

Ans: According to the law of universal gravitation, the force of gravity is proportional to mass. However, acceleration due to gravity (g) is independent of mass. So, when only gravity acts (free fall), all objects fall with the same acceleration (9.8 m/s²), irrespective of their mass. Air resistance may alter this, but in a vacuum, all fall equally.

12. What is the importance of the universal law of gravitation? Write any three points.

Ans: The universal law of gravitation explains:

(i) The force that binds us to Earth.

(ii) The motion of the moon around the Earth.

(iii) The motion of planets around the Sun.

(iv) The occurrence of tides due to the Moon and Sun.

13. Explain why it is easier to float in seawater than in river water.

Ans: Seawater is denser than river water due to dissolved salts. The buoyant force on a body is directly proportional to the density of the fluid. So, a person experiences a greater upward force in seawater, making it easier to float.

14. What do you understand by buoyancy? What factors affect buoyant force?

Ans: Buoyancy is the upward force exerted by a fluid on an object immersed in it.

Factors affecting buoyant force:

(i) Volume of object immersed in fluid.

(ii) Density of the fluid.

Greater volume or denser fluid increases buoyant force.

15. Explain why a coin sinks but a plastic bottle floats when placed in water.

Ans: The coin is denser than water, so its weight is greater than the upthrust. Hence it sinks.

A plastic bottle is less dense than water, so the upthrust is more than its weight. Hence, it floats.