**NIOS Class 10 Science & Technology Chapter 11 Solution – ****Gravitation**

NIOS Class 10 Science & Technology Solution Chapter 11 Gravitation. NIOS Class 10 Science & Technology Chapter 11 Question Answers Download PDF. NIOS Class 10 Science Notes.

**NIOS Class 10 Science & Technology Chapter 11 Solution**

Board |
NIOS |

Class |
10th (Secondary) |

Subject |
Science and Technology (212) |

Topic |
Question Answer, Solution, Notes |

**CHAPTER: – 11**

**(GRAVITATION)**

**INTEXT QUESTIONS 11.1**

**1) Why do two students sitting close to each other not feel force of gravitational attraction between them?**

**Ans: – **The force of gravitational attractions works on the direction form upward to inward direction which applicable vertical situated so in this as two friends are sitting apart from each other they don’t fell any force of attraction between them.

**2) Distance between two bodies is increased by a factor of four. How much willbe the change in the force of gravitation?**

**Ans: – **As we know gravitational force of attraction is inversely proportionate to the square of their distance so when the distance is increased then the force of gravitational also be decreased.

**3) Why is G known as universal gravitational constant?**

**Ans: – **The value is G is same anywhere in the universe so we call it as a universal gravitational constant.

**INTEXT QUESTIONS 11.2**

**1) What do you mean by acceleration due to gravity?**

**Ans: – **The acceleration due to gravity is the force of attraction between the different object to the earth magnetic field. Each object is binding this force of attraction of the earth.

**2) Why do a heavier and a lighter object when dropped from a same height fall at the same rate?**

**Ans: – **As we already read in that the acceleration due to gravity is same for the whole object which are present over the earth so when this two falling from a certain height will be at same rate.

**3) State SI unit of acceleration due to gravity.**

**Ans: – **The unite of acceleration due to gravity is m/s^2.

**4)Write equations of motion of an object moving under gravity.**

**Ans: – ** The equation of motion of the object moving under gravity is,

v = u + gt; s = ut +1/2 gt^2. And v^2 = u^2 + 2gs.

** **

**INTEXT QUESTIONS 11.3**

**1) Write two differences between mass of an object and its weight.**

**Ans: – **The mass of an object is the only the sum of masses of different particles present in it and the weight of any object is determined by the multiplication of the mass and the gravitational constant.

**2) State two factors on which weight of an object depends.**

**Ans: – **The weight of the object is depending on the mass of the object and acceleration due to gravity.

**3) What will be the weight of an apple while it is falling from a tree?**

**Ans: – **The weight of any free-falling body always be zero.

**INTEXT QUESTIONS 11.4**

**1) Hold a mug full of water inside a bucket filled with water. Now lift it above the surface of water. Why do you feel it is heavier now?**

**Ans: – ** When we lift any mug filled with the water above the surface of water then we feel heavy because of the acceleration due to gravity as the acceleration due to gravity is decreasing when height increased.

**2)Why does a piece of cork released under water bounce back?**

**Ans: – **There works an upward thrust on the cork when the water is released. So as a result of this forces the cork is released.

**3)What do you mean by buoyant force?**

**Ans: – **If we placed an object inside a water mug or any biker like substance then we can see that the object which is immersed in the pot is felt a force by water this force is known as buoyant force.

**4)Does the buoyant force act on a body when it is kept in vacuum?**

**Ans: – **The buoyant force worked only when any object is placed in water or in liquid.

**5)State two applications of Archimedes’ principle.**

**Ans: – **The submarine is placed in see by applying Archimedes principal and the lactomer also works in that principal.

**TERMINAL EXERCISE**

**1) State Newton’s law of gravitation.**

**Ans: – **Newton’s law of gravitation state the force of attraction between the masses of that object and the distance between them.

Or, F=Gm1 × m2/ r^2.

**2) How does the force of gravitation between two objects change when the distance between them is doubled?**

**Ans: – **As we all know gravitational force of attraction is depends inversely to the square of the distance between them so the when the distance will be double then the force will be 1/4^{th} of the previous one.

**3) How does the gravitational force between two objects change if the masses of both objects are doubled?**

**Ans: – **As, F=Gm1m2/r^2.

So, when masses are double then the force will be 4F.

**4) Derive an expression for the acceleration due to gravity on the surface of the earth in terms of earth’s mass, gravitational constant and radius of earth.**

**Ans: – **Let masses of two object is m1 and m2 and the distance between them is r.

So, according to Newton’s principal F~m1×m2 and F~1/r^2.

Then, F~m1×m2/r^2.

Or, F=Gm1×m2/ r^2. Where G is universal gravitational constant.

**5) Write the equations of motion of an object moving or falling only under gravity.**

**Ans: – **The equation of motion of an object moving or falling only under gravity is F=mg, where m=mass, g= acceleration due to gravity.

**6) What are the differences between the mass of an object and its weight? On what factors does the weight of an object depend?**

**Ans: – **The mass of an object is the only the sum of masses of different particles present in it and the weight of any object is determined by the multiplication of the mass and the gravitational constant.

This weight is depending on the gravitational acceleration and the height from the earth.

**7) Why does a capped empty plastic bottle released under water bounces back to the surface of water?**

**Ans: – **We all know that when an object is placed in water then the object deflects by the buoyancy forces of the water. For this reason, the plastic bottle released under water bounces back to the surface of water.

**8) What is force of buoyancy? What are the factors on which the magnitude of the buoyant force acting on a body at a given place depends?**

**Ans: – **When we place an object in liquid or water then the water or the liquid exert pressure on the object which is immersed in water this force is known as the buoyancy forces.

**9) State Archimedes’ principle. Give two applications of Archimedes’ principle.**

**Ans: – ** The Archimedes principal states that if a body is immersed in a fluid, then the body experiences an upward force which equal to the weight of the fluid displaced by it. This principal depends on

(i) density of the fluid and (ii) volume of the body immersed in the fluid.

**10) If the average distance between the earth and the sun is 1.5 × 1011 m, calculate the force of gravitation between the two. Given:**

**mass of the earth = 6 ×1024 kg**

**mass of the sun = 2 ×1030 kg**

**value of G = 6.7 ×10–11 Nm2kg–2.**

**Ans: – **The force of gravitation is, f=G×m1×m2/R^2.

Here, m1=6×10^24kg and m2=2×10^30kg, G=6.7×10^-11.R=1.5×10^11m.

Then, f=6.7×10^-11×6×10^24×2×10^30 / (1.5×10^11).

Or, f= 53.6×10^32 N.

**11)What is the mass of an object whose weight is 49N? (Given g = 9.8 ms–2).**

**Ans: – **We know, F=ma;

Where m=mass=? a=g=9.8 m/s^2. And F=force=49N.

So, 49=9.8×m.

Or, m=5kg.

**12) A stone is dropped from the top of a tower 45 m high. What is its velocitywhen it hits the ground? (Given g = 10 ms–2).**

**Ans: – **As, v^2 = u^2 + 2gh,

Where v=final velocity, u=initial velocity=0, g=10.

So, v^2 = 0 + 2×10×45;

Or, v=30.

**13) A body weighs 3.5 N in air and 2 N in water. How much buoyant force acts on the body?**

**Ans: – **The buoyant force= weight in air – weigh tin water,

Or, The buoyant force= 3.5 – 2=1.5N.

**14) A body is immersed in a liquid. If the liquid displaced by the body weighs 1 N then what is the buoyant force acting on the body?**

**Ans: – **We all know that the buoyancy force of an object is known as the amount of liquid displaced by uppers thrust which is 1N.

Buoyant force= liquid displaced by 1N force.