WBBSE Solutions For Class 8 School Science Chapter 1 Physical Environment Force Active Without Contact Review Questions

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Chapter 1 Physical Environment MCQ Questions

Question 1. If you have a mass of 40 Kg, then the force with which the earth attracts you towards its centre is

  1. 20 N
  2. 40 N
  3. 392 N
  4. 336 N

Answer: 3. 392 N

Question 2. If the mass of two objects is doubled, the force due to gravitation

  1. Increases by two times
  2. Increases by four times
  3. Decreases by four times
  4. Decreases by two times

Answer: 2. Increases by four times

Question 3. The mathematical expression of the Law of Universal Gravitation is

WBBSE Solutions for class 8 Physical Environment Section-2 Forces active without contact-mcq- 3

Answer:
WBBSE Solutions for class 8 Physical Environment Section-2 Forces active without contact-mcq- 3.

 

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4. Using a spring balance, we measure

  1. The mass of an object
  2. The weight of an object
  3. The pressure of an object
  4. The acceleration due to gravity at a place

Answer: 2. The weight of an object

Question 5. The weight of an object on earth is the product of its mass and

  1. G
  2. g
  3. Distance from the centre of the earth
  4. None of these

Answer: 2. g

Question 6. F (the gravitational force) is zero when the distance between two objects is

  1. Zero
  2. Infinitely large
  3. Less than the radius of the earth
  4. Does not depend on the distance between the two objects

Answer: 2. Infinitely large

Question 7. The magnitude of escape velocity is

  1. 11.2 km/s
  2. 11.2 m/s
  3. 11.2 cm/s
  4. 11.2 km/h

Answer: 1. 11.2 km/s

8. The value of G in SI unit is

Question 9. If the acceleration due to gravity on earth is “g”, its value on the moon is

  1. g/6
  2. g
  3. 6g
  4. 0

Answer: 1. g/6

Question 10. When an ebonite rod is rubbed with wool, it acquires

  1. Negative charge
  2. No charge
  3. Positive charge
  4. Protons

Answer: 1. Negative charge

Question 11. Keeping masses of two bodies constant, if the distance between them is made twice then the gravitational force of attraction between them becomes

  1. Twice the previous
  2. Four times the previous
  3. Half of previous
  4. A fourth of previous

Answer: 2. Four times the previous

Question 12. The weight of a freely falling object

  1. Gradually increases
  2. Gradually decreases
  3. Remains same
  4. Vanishes

Answer: 3. Gradually decreases

Question 13. The net charge in an atom is

  1. Negative
  2. Zero
  3. Positive
  4. None of these

Answer: 2. Zero

Question 14. Two identical metal spheres A and B are placed on insulating stands and kept in contact as shown. What kind of charges will appear on A and B when a negatively charged ebonite rod is brought near A ? Ebonite rod

WBBSE Solutions for class 8 Physical Environment Section-2 Forces active without contact-mcq- 14

  1. Both A and B will have a positive charge
  2. Both A and B will have a negative charge
  3. A will have a negative charge and B a positive charge
  4. A will have a positive charge and B a negative charge

Answer: 4. A will have a positive charge and B a negative charge

Question 15. The CGS unit of charge is

  1. Coulomb
  2. Statcoulomb
  3. E.S.U.
  4. Ampere

Answer: 3. E.S.U.

Question 16. An atom is electrically neutral because

  1. The number of protons is the same as the number of electrons
  2. The number of protons is the same as the number of neutrons
  3. The number of neutrons is the same as the number of electrons
  4. Atom does not exhibit static electricity

Answer: 1. Number of protons is the same as the number of electrons

Question 17. Keeping the distance between the two point- charges fixed, if the amount of charge on the point charges increases,

  1. The electrostatic force increases
  2. The electrostatic force decreases
  3. The electrostatic force remains unchanged
  4. It is independent of the magnitude of charges

Answer: 1. The electrostatic force increases

Question 18. The magnitude of the electrostatic force between two point charges

  1. Depends on the intervening medium
  2. Is independent of the distance between them
  3. Is independent of the charge on the point- charges
  4. All of these

Answer: 1. Depends on the intervening medium

Question 19. When no charge is supplied to or removed from a neutral body, then the amount of

  1. Positive charge > negative charge present in it
  2. Positive charge < negative charge present in it
  3. Positive charge = negative charge present in it
  4. No charge is present in the body initially

Answer: 3. positive charge < negative charge present in it

Question 20. The law of gravitation gives the gravitational force between

  1. Earth and the sun only
  2. Earth and point mass only
  3. Two charged bodies only
  4. Any two bodies having a certain mass

Answer: 4. Any two bodies having a certain mass

Question 21. Two objects of different masses falling freely near the surface of the moon would

  1. Have the same velocities at any instant
  2. Have different accelerations
  3. Experience forces of different magnitudes
  4. undergo different distances at the same interval of time

Answer: 1. Have the same velocities at any instant

Chapter 1 Physical Environment Fill in the Blanks

Question 1. The earth pulls any object near it by the force of _______.
Answer: Gravity

Question 2. Weight = mass of an object x _______
Answer: Acceleration due to gravity

Question 3. The magnitude of “g” in SI unit is _______
Answer: 9.8m/s²

Question 4. The magnitude of “g” in the CGS unit is _______
Answer: 981 cm/s²

Question 5. The magnitude of “g” _______is than at the equator.
Answer: Less

Question 6. Speed of a freely falling body _______ at the poles with the increase in the time of fall.
Answer: Increases

Question 7. The distance traversed by a freely falling body _______ with the increase in time of fall.
Answer: Increases

Question 8. If the mass of one object is 2 kilograms, its weight is _______ Newton.
Answer: 19.6

Question 9. Electrons are _______ charged particles
Answer: Negative

Question 10. Like charges _______ each other.
Answer: Repel

Question 11. Unlike charges _______ each other.
Answer: Attract

Question 12. Statcoulomb is the unit of _______
Answer: Charge

Question 13. Keeping the number of charges on two-point- charges fixed, if the distance between them is increased, the electrostatic force will _______
Answer: Decreases

Question 14. When a glass rod is rubbed with a piece of silk it acquires_____charge.
Answer: Positive

Question 15. When an ebonite rod is rubbed with wool, it acquires _______ charge.
Answer: Negative

Question 16. All the positive charges of an atom are contained in the _______
Answer: Nucleus

Question 17. If an atom loses an electron it becomes _______ charged.
Answer: Positively

Question 18. If an atom gains an electron, it becomes _______ charged.
Answer: Negatively

Chapter 1 Physical Environment Identify as ‘True’ or ‘False’

Question 1. When an object is thrown upwards, it comes down due to gravity.
Answer: True

Question 2. The force of gravitation can never be zero.
Answer: True

Question 3. G is called the Universal gravitational constant.
Answer: True

Question 4. The magnitude of “G” is affected by heat, light, magnetic or electric fields etc.
Answer: True

Question 5. The force of gravity on unit mass is equal to the acceleration dile to gravity.
Answer: True

Question 6. The unit of “G” in the CGS unit is dyne.cm² /g².
Answer: False

Question 7. Force always produces acceleration in the body on which it is applied.
Answer: False

Question 8. The value of “G” in the SI unit is 6.67/ 108 dyne.cm² / g²
Answer: False

Question 9. Spring balance is used to measure the weight of an object.
Answer: True

Question 10. The average value of “g” in SI unit is 9.8 m/s².
Answer: True

Question 11. In a vacuum, all bodies starting from rest fall with equal rapidity.
Answer: True

Question 12. In absence of any resistance, a heavier object will fall more rapidly than a lighter object.
Answer: False

Question 13. Earth always produces the same acceleration on every object.
Answer: True

Question 14. Electrons are positively charged.
Answer: False

Question 15. Neutrons are negatively charged.
Answer: False

Question 16. Rubbing two objects against each other may produce static electricity.
Answer: True

Question 17. A freely falling body is weightless.
Answer: True

Question 18. If the magnitude of two-point charges is doubled, the electrostatic force will increase by 4 times.
Answer: True

Question 19. Repulsion is a surer test of electrification.
Answer: True

Question 20. Gravitational force is operational between an electron and a proton.
Answer: False

Chapter 1 Physical Environment Match the Columns

Question 1.

 Column – A Column – B
A. Law of Universal Gravitation 1. Galileo
B. Laws of freely falling bodies 2. Newton
C. Naming of different charges as positive and negative 3. Leaning tower of Pisa
D. Experiment with falling objects 4. Franklin

Answer: A-2,B-1,C-4,D-3

Question 2.

 Column – A Column – B
A. g 1. Unit of charge
B. G 2. 11.2 km/s
C. Coulomb 3. 9.8 m/s2
D. Escape velocity 4. 6.67/1011 N.m2/kg2

Answer: A-3,B-4,C-1,D-2

Question 3.

Column – A Column – B
A. Increase of altitude 1. G unchanged
B. Increase in distance between two objects 2. Force of gravitation
C. Decrease in distance between two objects 3. Decrease in gravitation
D.  Increase in mass of two objects 4. Force of increases

Answer: A-3,B-3,C-2,D-2

Question 4.

Column – A Column – B
A. CGS unit of “g” 1. cm
B.  SI unit of 2. coulomb
C. SI unit of charge 3. N.m2/kg2
D. CGS unit of distance 4. cm/s2

Answer: A-4,B-3,C-2,D-1

Question 5.

Column – A Column – B
A. w = 1. G r2 m2
B. F = 2. k q1q2/r2
C. The electrostatic force of attraction 3. m.g
D. g = 4. w/m

Answer: A-3,B-1,C -2,D-4

 

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