Force and Motion
I am Abid Ali Fakir, the digital creater, freelancer and YouTuber. In this blog we collected questions from different publication, especially Asmita publication from chapter Force and Motion (Chapter wise ). We tried out best to provide answers to the questions.
For nepali use Google translater by clicking tap section .
Very short questions.
1.What change occurs in the gravitational force between two bodies when their masses are kept constant and the distance between their centres is reduced by 3 times?
Ans: Gravitation force increase by 9 times when we kept masses constant and reduced distance by 3 times.
2. Which formula will you use to find out the height from the Earth's surface from where a stone dropped down and time taken by stone to reach the ground?
Solution,
h= ut+ 1/2*gt^2
Where:
h is the height.
g is the acceleration due to gravity.
t is the time taken to reach the ground.
u=initial velocity
3. What is the value of g in the surface of moon?
Ans: The value of g in the surface of moon is 1.625 m/s^2
4. If 'm' is mass and 'W' is weight, write down relation between 'm' and 'W'.
Ans: The relation between mass and weight is directly proportional i.e.
W = m x g
5. What is the value of acceleration due to gravity of the earth on equator?
Ans: The value of acceleration due to gravity of the earth in equator is 9.78 m/s^2
6. State Newton's Universal law of gravitation.
Ans: Every objects in the universe attract each other with the force that is directly proportional to the product of masses and inversely proportional to their square distance called Newton's law of gravitation.
Mathematicaly:
F = Gm1m2/ d^2
7. What is the unit of Universal gravitational constant?
Ans: The S.I unit of Universal gravitational constant is Nm^2/kg^2
8. What is the acceleration due to gravity on the surface of Jupiter?
Ans: Approximately 24.5 m/s^2 is the acceleration due to gravity on the surface of Jupiter.
9. Define free fall.
Ans: Free fall is the motion of a body when it is falling solely under the influence of gravity, with no other forces acting on it, such as air resistance.
During free fall, an object accelerates at a constant rate, which is the acceleration due to gravity.
10. Define gravity.
Ans: The force by which object attract each other is called gravity.
11. Define Universal gravitational constant.
Ans: The Universal Gravitational Constant, denoted by 𝐺 is a constant used in the formula for calculating the force of gravity between two objects.
Its value is approximately 6.674×10^−11 N(m²/kg²)
12. What is the relation between gravitational force and the distance between two bodies?
Ans: The relation between gravitational force and the distance between two bodies is inversely proportional to its distance.
Mathematicaly:
F inversely 1/d^2
13. What is the value of acceleration due to gravity at the center of the earth?
Ans: At the center of the Earth, the acceleration due to gravity 𝑔, g is effectively zero.
This is because the gravitational forces from all parts of the Earth cancel out at the center, resulting in no net gravitational force.
14. What is an acceleration due to gravity?
Ans: Acceleration due to gravity is the rate at which an object speeds up as it falls freely towards the Earth.
15. What is the value of g on equatorial region and polar region of the earth?
Ans: The value of 'g' on equator is 9.7m/s^2 and on polar is 9.8m/s^2.
16. What is weightlessness?
Ans: Weightlessness occurs when an object experiences free fall or is in a state of continuous free-fall orbit around a celestial body, such as Earth.
17. In which condition will acceleration due to gravity of parachute be zero?
Ans:
पैराशूटको गीरिरहेको अवस्थामा, गीरावटको त्वरण कहिल्यै शून्य हुँदैन जबसम्म यो पृथ्वीको गुरुत्वाकर्षण क्षेत्र भित्र छ। यद्यपि, पाराशूटले सन्तुलनको स्थितिमा पुग्न सक्छ जहाँ कुल त्वरण शून्य हुन्छ। यो अवस्था तब आउँछ जब माथि हावा प्रतिरोधको बल (ड्राग) र तलको गुरुत्वाकर्षण बल बराबर हुन्छ। यस अवस्थामा, पाराशूट स्थिर वेगमा गीरिन्छ, जसलाई टर्मिनल वेग भनिन्छ, तर गुरुत्वाकर्षणको त्वरण लगभग
9.8m/s ^2 स्थिर रहन्छ।
18. What is gravitaion?
Ans The force by which every body attract each other is called gravitaion.
19. How does the distance between two objects affect the gravitational force between them?
Ans: As we know that gravitational force (F) inversely proportional to its square distance. It means that when we increase distance then F will decrease and vice versa.
20. Name one factor that affect the value of acceleration due to gravity.
Ans: Acceleration due to gravity is affected by the quantity of body's mass.
Another factor 'g' get affected with square of radius of body.
Short Question
1. Prove that unit of gravitational constant is derived unit.
Ans: Download pdf for answer.
2. Mass of a body is constant but weight varies from place to place. Why?
Ans: Mass of a body is constant but weight varies from place to place because weight depends upon acceleration due to gravity 'g' and the value of g is varies from place to place .
3. Acceleration due to gravity of an object is -9.8m/s^2. Write two pieces of information that can be obtained by this statements.
Ans: If acceleration due to gravity is stated as −9.8m/s^ , it indicates negative direction and decrease of acceleration
Details:
Direction: The negative sign represents that gravity is acting downward, towards the center of the Earth, in the direction opposite to the positive direction assumed in the coordinate system.
Deceleration in Upward Motion: If an object is moving upward, the acceleration due to gravity will act to reduce its speed by 9.8m/s^2 every second until it reaches its peak height and starts descending.
दिशा: नकारात्मक चिह्नले गुरुत्वाकर्षण तलको दिशामा काम गरिरहेको दर्शाउँछ, अर्थात् पृथ्वीको केन्द्रतर्फ, समन्वय प्रणालीमा मान्यता प्राप्त सकारात्मक दिशाविपरीत।
उपरको गति कम हुनु: यदि कुनै वस्तु माथि जाँदै छ भने, गुरुत्वाकर्षणको त्वरण यसको गति प्रत्येक सेकेण्डमा
9.8 m/s^2 ले घटाउँछ, जबसम्म यो शीर्ष उचाइमा पुगेर तल झर्छ।
4. By how many times the weight of a body less in the surface of the moon than on the surface of the earth? Why?
Ans: The weight of a body is 1/6 times lees than earth because acceleration due to gravity of the moon is 1.6m/s^2 due to which weight on the moon decrease by 1/6 times.
5. Write two condition for an object to have zero weight.
Ans: The condition for an object to have zero weight are
1. When object is in free fall condition
2. When object is in space with no gravitational force.
6. Kathmandu lies at a higher altitude than Biratnagar from sea level. Where does an object has more weight between these two places? Give reason.
Ans: In Biratnagar, weight of the body is more than Kathmandu because as we know that acceleration due to gravity inversely proportional to is square of (R+h) . It means that when (R+h) increase value of 'g' gets decrease.
7. When a man travs from Hilly region to terai region, what will happen to his weight? Explain with reason.
Ans: When a man travel from Hilly to terai region then it's weight slightly decrease because weight is directly proportional to acceleration due to gravity and acceleration due to gravity get increased at low altitude.
8. Why is the value of acceleration due to gravity (g) more in terai region than in mountain?
Ans: The value of acceleration due to gravity more in terai region than mountain because terai is at low altitude and mountain is at higher altitudes and we know 'g' decrease with altitude and increase with low altitude.
9. Why does the weight of the body differ on different celestial bodies in the universe?
Ans: The weight of the body differ on different celestial bodies in the universe because different celestial bodies has different mass and acceleration due to gravity due to which it's weight differ from bodies to bodies
10. Astronaut feels weightlessness inside spacecraft. Why?
Ans: Astronaut feels weightlessness inside spacecraft because there is no external contact force pulling or pushing upon their bodies.
11. A large stone of 20 kg mass and a small stone of 5 kg mass are dropped simultaneously from certain height. Which one teach on the ground first. Why?
Ans: Large stone of 20 kg mass dropped first then small one because large stone experience less air resistance .
12. What happens to the weight of an object when it is taken from earth to the moon.Why?
Ans: The weight of an object decreased when we take body from earth to moon because acceleration due to (g) of the moon is 1.62 m/s^2 . And we know that 'W' directly proportional to 'g' due to which it's value get decreased by 6 times.
13. The acceleration due to gravity of Jupiter is 25 m/s^2, what does it mean?
Ans: The acceleration due to gravity of Jupiter is 25 m/s^2,it means that when any object dropped in the surface of Jupiter it accelerate at the rate of 25m/s^2.
14. Write the reason behjnd the atmosphere does not escape away from the earth.
Ans: Due to gravity atmosphere doesn't escape away from the earth.
15. Give reason, why an iron ball and a feather fall together in vacuum?
Ans: When an iron ball and feather fall together in vacuum because in vacuum there is no air resistance and in the absence of air resistance, acceleration due to gravity act equally in both body.
16. The value of acceleration due to gravity of moon is 1.67 m/s^2. What does it mean?
Ans: The value of acceleration due to gravity of the moon is 1.67m/s^2 , it means that when we dropped any object on the surface of the earth it accelerate at the rate of 1.67m/^2.
17. The weight of a body is more at polar region than at equator of the earth. Give reason.
Ans: The weight of a body is more at polar region than at the equator of the earth because the value of 'g' is more at polar region and less in equator and we know, weight directly proportional to g. The more 'g' more weight.
18. Why can't we fall safely with the help of parachute towards the moon?
Ans: We can't fall safely with the help of parachute towards the moon because acceleration due to gravity of the moon is very low due to which parachute not work.
19. What change occurs in the gravitational force between two bodies when mass if each body is made double and distance between their center is halved.
Ans: Download pdf for answer
20. State Newton's law of gravitation.
Ans: Download pdf for answer
21. Under what conditions is the value of gravitational force equal to the gravitational constant (F=G)?
Ans: When products of their masses become equals to square of distance between them then Gravitational force 'F' and Gravitational Constant 'G' become equal.
22. Write down the effects of gravitation force.
Ans: The effects of gravitation force are
1. The force of gravity keeps all of the planets in orbit around the sun.
2. Gravity makes waves that move at light speed.
3. The Moon's gravity pulls on the Earth and makes the tides rise and fall every day.
4. without gravity the earth will be destroyed.
23. Mathematicaly present the difference in the gravitational force between two objects when the mass of each is made double and the distance between them is made one-fourth their initial distance.
Ans: Download pdf for answer
24. A student suggest a trick for gaining Profit in a business. He suggests buying orange from the mountain and selling them to Terai at the cost price. If a beam balance is used during transaction, explain based on scientific fact, whether his trick goes wrong or right .
Ans: His trick goes wrong because when beam balance used at the time transaction, it calculate mass not weight and mass of the body is same everywhere in the universe.
25. A piece of the stone and feather are dropped from the same height at the lunar surface, which one will reach on the surface fast and why?
Ans: When we dropped stone and feather at the surface of the moon then both objects will reach at the same time because there is no air resistance.
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