CBSE Questions for Class 8 General Knowledge Basic Science Quiz 3 - MCQExams.com

Fahrenheit and Celsius are the two scales used for measuring temperature. If the numerical value of a temperature recorded in both the scales is found to be same, what is the temperature? 
  • $$-40^o$$
  • $$+40^o$$
  • $$+72^o$$
  • $$-72^o$$
Which one of the following statements is not correct?
  • The SI unit of charge is ampere-second
  • Debye is the unit of dipole moment
  • Resistivity of a wire depends on its length and breadth 
  • The kinetic energy of an electron of mass m kg and charge e coulomb, when accelerated through a potential difference of V volt, is eV joule
With respect to the new initiative by the government regarding air pollution - AQI, choose the correct statement(s). 
It aims to monitor the air quality of four metro cities only.
It is a real-time measuring process.
Dark red colour indicates the severe condition of air quality.
Select the correct answer using the codes given below.
  • 1 and 3
  • Only 3
  • 1, 2 and 3
  • 2 and 3
Match List I with List II and select the correct answer using the code given below the Lists: 
List I
(Element)		List II
(Use)
A. LiTime keeper in atomic clocks
B. NaBatteries
C. KTransfer of nerve impulses
D. CsControl of the water content in the blood
  • A-2, B-3, C-4, D-1
  • A-1, B-2, C-3, D-4
  • A-2, B-4, C-3, D-1
  • A-1, B-3, C-2, D-4
Which component  is formed by plants in the ecosystem ________________.
  • Decomposer
  • Consumer
  • Producer
  • All of the above
Which of the following pairs is wrong?
  • Pressure - Barometer
  • Relative density - Pyrometer
  • Temperature - Thermometer
  • Earthquake - Seismograph
Match the columns:
List I (Quantity)List II (Unit)
(A) Luminous intensity(1) Kelvin
(B) Amount of substance(2) Candela
(C) Time(3) Second
(D) Temperature(4) Mole
  • A-2; B-4; C-3; D-1
  • A-4; B-2; C-3; D-1
  • A-2; B-4; C-1; D-3
  • A-3; B-1; C-4; D-2
Match the columns:
QuantityDimensions
(A) Velocity(1) $$\left[ ML{ T }^{ -2 } \right] $$
(B) Force(2) $$\left[ L{ T }^{ -1 } \right] $$
(C) Work(3) $$\left[ M{ L }^{ 2 }{ T }^{ -2 } \right] $$
(D) Momentum(4) $$\left[ ML{ T }^{ -1 } \right] $$
  • A-2; B-1; C-3; D-4
  • A-3; B-4; C-1; D-2
  • A-2; B-1; C-4; D-3
  • A-4; B-3; C-2; D-1
The displacement of a particle at time is given by
$$x=aj+bj+\cfrac { c }{ 2 } { t }^{ 2 }k$$
where $$a,b,c$$ are positive constants. Then the particle is _________.
  • accelerated along k-direction
  • decelerated along k-direction
  • decelerated along j-direction
  • accelerated along j-direction
The SI unit of acceleration is _______.
  • $${ ms }^{ -1 }$$
  • $${ ms }^{ -2 }$$
  • $$c{ ms }^{ -2 }$$
  • $$k{ ms }^{ -2 }$$
Masses of stars and galaxies are usually expressed in terms of _______.
  • neutron mass
  • earth's mass
  • solar mass
  • lunar mass
Which of the following physical quantities is dimensionless?
  • Strain
  • Angle
  • Specific gravity
  • All of these
Consider the physical quantities
(1) Electric current  (2) Work
(3) Temperature       (4) Density
Which of the above are scalar quantities?
  • 1, 2 and 3
  • 1. 4 and 3
  • 3, 4 and 2
  • 1, 2, 3 and 4
One light year is approximately equal to ________.
  • $${10}^{11}km$$
  • $${10}^{15}m$$
  • $${10}^{16}m$$
  • $${10}^{16}km$$
If the density of water is $$1g\,{cm}^{-3}$$  in CGS system, its value in MKS system is __________.
  • $$1$$ $$kg$$ $${m}^{-3}$$
  • $${10}^{3}$$ $$kg$$ $${m}^{-3}$$
  • $${10}^{-3}$$  $$kg$$ $${m}^{-3}$$
  • $${10}^{-6}$$ $$kg$$ $${m}^{-3}$$
The force required to keep a body in uniform circular motion is ________.
  • centripetal force
  • centrifugal force
  • resistance
  • None of these
The motion of a car along a straight path is shown by the following figure.
The car starts from $$O$$ and reaches at $$A$$, $$B$$ and $$C$$ at different instants of time. During its motion from $$O$$ to $$C$$ and back to $$B$$, the distance covered and the magnitude of the displacement are respectively
733203_8c6f0a05ff074e1f8d7e4696e614e3c5.png
  • $$25km$$ and $$60km$$
  • $$95km$$ and $$35km$$
  • $$60km$$ and $$25km$$
  • $$85km$$ and $$35km$$
Consider the following statements.
(1) All plane angles are measured in radian.
(2) All the solid angles are measured in steradian.
Which of the following statements given above is/are correct?
  • Only 1
  • Only 2
  • 2 and 3
  • 1,2, and 3
Two stones of unequal masses are thrown vertically up with the same velocity. Which of the following will happen?
  • The heavier mass will reach greater height
  • The lighter mass will reach greater height
  • Both will reach the same height
  • Any of them may reach greater height
A person is sitting in a moving train and facing the engine. He tosses up a coin and coin falls behind him. It can be concluded that the train is _________.
  • moving forward and gaining speed
  • moving forward and losing speed
  • moving forward with uniform speed
  • moving backward with uniform speed
A piece of paper and a cricket ball are dropped from the same height. Under which of the following conditions do both reach the surface simultaneously?
  • They must have the same volume
  • They must have the same density
  • They must have the same mass
  • They must be dropped in vacuum
For a particle revolving in a circular path with constant speed, the acceleration of the particle is __________.
  • along the tangent
  • along the radius
  • zero
  • along the circumference of the circle
For a moving body, at any instant of time, __________.
  • if the body is not moving, the acceleration is necessarily zero
  • if the body is slowing, the retardation is negative
  • if the body is slowing, the distance is negative
  • if displacement, velocity and acceleration at that instant are known, we can find the displacement at any given time in future
Which one of the following statements is not correct?
  • If the velocity and acceleration have opposite sign, the object is slowing down
  • If the velocity is zero at an instant, the acceleration should also be zero at that instant
  • If the velocity is zero for a time interval, the acceleration is zero at any instant within the time interval
  • So,the position and velocity have opposite sign the object is moving towards the origin
If the distance $$S$$ covered by a moving car in rectilinear motion with a speed $$v$$ in time $$t$$ is given by $$S=vt$$, then the car undergoes ___________.
  • a uniform acceleration
  • a non-uniform acceleration
  • a uniform velocity
  • a non-uniform velocity
A body has a free fall from a height of $$20m$$. After falling through a distance of $$5m$$, the body would have ___________.
  • lost one-fourth of its total energy
  • lost one-fourth of its potential energy
  • gained one-fourth of its potential energy
  • gained three-fourth of its total energy
A brick is thrown vertically from an aircraft flying two kilometers above the Earth. The brick will fall with a ________.
  • constant speed
  • constant velocity
  • constant acceleration
  • constant speed for some time then with constant acceleration as it nears the Earth
Assertion (A) Pulling a lawn roller is easier than pushing it.
Reason, (R) Pushing increases the apparent weight and hence the force of friction.
  • Both A and R are true and R is the correct explanation of A
  • Both A and R are true and R is not the correct explanation of A
  • A is true, but R is false
  • A is false, but R is true
Water flows out of the hole of a bucket and follows a parabolic path. If the bucket falls freely under gravity, the water flow (ignoring air resistance) ___________.
  • follows a straight line path relative to the falling bucket
  • follows a parabolic path relative to the falling bucket
  • stops
  • decreases but continues to flow
A motor vehicle is moving on a circle with a uniform speed. The net acceleration of the vehicle is ________.
  • zero
  • towards the centre of the circle
  • away from the centre along the radius of the circle
  • perpendicular to the radius and along the velocity
0:0:1


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