Top 30 Physics MCQs for Competitive exams

பல்வேறு போட்டித் தேர்வுகளில் இயற்பியல் முக்கியப் பங்காற்றுகிறது, விண்ணப்பதாரர்களுக்கு அவர்களின் தயாரிப்பில் உதவ, நாங்கள் 30 கேள்விகளை (MCQs) தொகுத்துள்ளோம். உங்கள் இயற்பியல் அறிவை மேம்படுத்துவதற்கும், வரவிருக்கும் தேர்வுகளுக்கு உங்களை சிறப்பாக தயார்படுத்துவதற்கும் ஒவ்வொரு கேள்விக்கும் சரியான பதில் உள்ளது.

Top 30 Physics MCQs

Q1.What is the relationship between acceleration and velocity?

(a) Acceleration is the rate of change of velocity

(b) Velocity is the rate of change of acceleration

(d) Acceleration is the speed of an object

Q2.During __________ motion of an object along a straight line, the change in velocity of the object for any time interval is zero.

(a) Linear

(b) Translational

(d) Uniform

Q3.A body of mass 5 kg accelerates from 12 m/s to 20 m/s in 4 seconds due to the application of a force on it. Calculate the magnitude of this force (in N).

(a) 40

(b) 10

(d) 80

Q4. Which of the following is an example of non-uniform motion?

(a) A car driving at a constant speed on a straight road

(b) A ball bouncing off a wall

(d) A car driving around a circular track

Q5.If the Distance-Time graph is a curve then it represents ____________.

(a) uniform speed

(b) constant displacement

(d) non-uniform speed

Q6. In the equation of motion 2as = v2 – u2, where “s” represents _________________.

(a) Speed

(b) Displacement

(d) Acceleration

Q7. The shortest distance measured from the initial to the ﬁnal position of an object is known as the _____________.

(a) Motion

(b) Direction

(d) Displacement

Q8. If a body is moving on a circular path, what is its average velocity if it completes one cycle in one second?

(a) Average velocity depends upon time taken to complete one cycle

(b) One

(d) Zero

Q9.Which of the following is an example of circular motion?

(a) A ball rolling down a hill

(b) A car driving in a straight line

(d) A bird flying in a straight line

Q10. According to Newton’s first law, what will happen to a ball thrown horizontally on a frictionless surface?

(a) The ball will continue to move horizontally at a constant speed

(b) The ball will slow down and eventually stop

(d) The ball will change direction

Q11. The SI unit of G, the universal gravitation constant is ______________.

(a) N m2 kg2

(b) N m2 kg-2

(d) N m-2 kg2

Q12. If the acceleration due to gravity on the surface of earth is g, then the acceleration due to gravity on the surface of a planet whose mass is same as that of earth and radius is half as that of earth is _________________.

(a) 2g

(b) g/4

(d) 4g

Q13.A force of 200 N displaces a body by 4 m, calculate the work done (in J).

(a) 40

(b) 500

(d) 800

Q14.The gravitational force of attraction between two bodies is _______________ the distance between the two bodies.

(a) Inversely proportional to the

(b) Directly proportional to the square of

(d) Directly proportional to the

Q15.The value of acceleration due to gravity (g) __________________.

(a) is greater at the poles than at the equator

(b) is lesser at the poles than at the equator

(d) is greater at the South pole than at the North pole

Q16. Any body kept in a fluid experiences an upward force called _____________.

(a) Torque

(b) Moment

(d) Upthrust

Q17.The product of force and the time for which the force acts on a body is equal to the change in_______________ of the body.

(a) Acceleration

(b) Torque

(d) Velocity

Q18. If a force acts upon two objects at rest, and having different masses for the same amount of time, then which one of the following will be the same for both the objects?

(a) Acceleration

(b) Kinetic Energy

(d) Momentum

Q19. If the radius of the earth decreases and its mass remains the same, then the value of “acceleration due to gravity” will _____.

(a) decrease

(b) increase

(d) become zero

Q20. The sensation of weightlessness in a spacecraft in an orbit is due to the –

(a) Absence of gravity outside

(b) Acceleration in the orbit which is equal to the acceleration due to gravity outside

(d) Spacecraft in the orbit has no energy

Q21. Find the resistance (in Ω) of a wire of length 20m, cross-sectional area 1 cm2 and made of a material of resistivity 200 Ωm.

(a) 40

(b) 4000

(d) 2000

Q22.What is the heat released by a heating filament rated 20 W when it is kept on for 2 seconds?

(a) 40

(b) 10

(d) 20

Q23.What is the heat generated (in J) in a heating element of resistance 900 Ω when a current of 0.3 A passes through it for 10 seconds?

(a) 2700

(b) 810

(d) 1350

Q24. What is the resistance (in Ω) of an electrical component if a current of 0.4A passes through it on application of 12 V of potential difference across it?

(a) 4.8

(b) 60

(d) 30

Q25.What is the heat released by a heating filament rated 24 W when it is kept on for 6 seconds?

(a) 4

(b) 144

(d) 8

Q26.What is the power rating (in W) of a bulb if a current of 0.1A passes through on application of 250V of potential difference across its terminals?

(a) 2500

(b) 50

(d) 1250

Q27. The heating effect in a heating coil is directly proportional to

(a) I

(b) R2

(d) √R

Q28. A 100 watt electric bulb is used for 10 hours. What will be the cost of electricity consumed, if the consumption cost is Rs. 5 per unit?

(a) Rs. 5

(b) Rs. 10

(d) Rs. 50

Q29. Which of the following is NOT based on the heating effect of current?

(a) Electric iron

(b) Electric bulb (with filament)

(d) Microwave

Q30. Electric motors operating at low voltages tend to burn out because-

(a) They draw more current which is inversely proportional to the voltage.

(b) They draw more current which is inversely proportional to the square root of the voltage.

(d) Low voltage sets in electrical discharge.

Solution:

S1.Ans(a)

Sol. Acceleration and velocity are both concepts used to describe the motion of an object. Velocity refers to the rate at which an object changes its position with respect to time, while acceleration refers to the rate at which an object’s velocity changes with respect to time.

In other words, acceleration is the rate of change of velocity over time. If an object’s velocity is changing, then it is said to be accelerating. The direction of the acceleration is determined by the direction of the change in velocity.

Mathematically, acceleration is defined as the derivative of velocity with respect to time:

a = dv/dt

where “a” is acceleration, “v” is velocity, and “t” is time.

S2.Ans.(d)

Sol. During uniform motion of an object along a straight line, the change in velocity of the object for any time interval is zero.

Linear Motion – Linear motion refers to the motion of an object in a straight line. In other words, the object moves along a path that does not curve or change direction. This is also sometimes referred to as rectilinear motion.
Translational Motion – Translational motion refers to the motion of an object where all points on the object move along parallel paths in the same direction, without any rotation or angular motion. In other words, translational motion is the motion of an object where all points on the object move the same distance in the same direction.
Equilibrium Motion – Equilibrium motion refers to the motion of an object where the net force acting on the object is zero, and as a result, the object does not accelerate. In other words, the object is in a state of balance, and its motion is constant, without any changes in speed or direction.

S3.Ans.(b)

Sol. We know that

Accelaration = (Final Velocity- Initial Velocity)/time

i.e. a = (v-u)/t

= (20-12)/4

= 2 m/sec2

Now, Force= Mass ×Acceleration

F = ma

= 5×2 = 10 N.

S4.Ans(d)

Sol. A car driving around a circular track. Non-uniform motion is motion with a changing velocity, and a car driving around a circular track is an example of non-uniform motion because its velocity is constantly changing.

S5.Ans.(d)

Sol. If the Distance-Time graph is a curve then it represents non-uniform speed. The slope of distance–time graph represents its velocity.

S6.Ans.(b)

Sol. Third Equation of Motion

v2 = u2 +2as

Where s is the displacement, a is the acceleration, u and v are initial and final velocity respectively.

Other Equation of Motion:

First equation of motion: v = u + at. This equation relates the final velocity (v) of an object to its initial velocity (u), acceleration (a), and time (t) taken to change velocity.
Second equation of motion: s = ut + 1/2 at2. This equation relates the distance (s) traveled by an object to its initial velocity (u), acceleration (a), and time (t) taken to travel that distance.
Third equation of motion: v2 = u2 +2as. This equation relates the final velocity (v) of an object to its initial velocity (u), acceleration (a), and distance (s) travelled.

S7.Ans.(d)

Sol. The shortest distance measured from the initial to the ﬁnal position of an object is known as the displacement.

Direction – Distance refers to the total path travelled by an object in motion. It is a scalar quantity, which means it has only magnitude (size) and no direction.
Velocity – Velocity is a physical quantity that describes the rate of change of an object’s position with respect to time. It is a vector quantity, which means it has both magnitude (speed) and direction.

S8. Ans.(d)

Sol. When a body is moving on a circular path its average velocity when it complete one cycle in one second is zero.

S9.Ans(c)

Sol. A merry-go-round spinning. Circular motion is motion in a circular path around a central point, and a merry-go-round spinning is a classic example of circular motion.

S10.Ans(a)

Sol. The ball will continue to move horizontally at a constant speed. According to Newton’s first law, an object in motion will stay in motion with a constant velocity unless acted upon by an external force. If there is no friction to slow down the ball, it will continue to move horizontally at a constant speed.

Newton’s Laws of Motion:

Newton’s First Law of Motion: Also known as the law of inertia, it states that an object at rest will remain at rest, and an object in motion will continue to move at a constant velocity in a straight line, unless acted upon by an external force. This means that objects have a natural tendency to resist changes in their state of motion, and only external forces can cause them to accelerate or decelerate.
Newton’s Second Law of Motion: This law deals with the relationship between force, mass, and acceleration. It states that the acceleration of an object is directly proportional to the net force acting on it, and inversely proportional to its mass. In other words, F=ma, where F is the net force, m is the mass of the object, and a is the acceleration it experiences.
Newton’s Third Law of Motion: This law states that for every action, there is an equal and opposite reaction. This means that whenever one object exerts a force on another object, the second object exerts an equal and opposite force back on the first object. This law is often summarized as “For every action, there is an equal and opposite reaction.

S11. Ans.(b)

Sol. SI unit of G =Nm2kg-2.

As per universal law of gravitation,

where:
F: Gravitational force, whose SI unit is Newton (N)
d: Distance between the masses, whose SI unit is metre (m)
M, m: Masses whose SI unit is kg.

Therefore, the SI unit of G is: Nm2kg−2.

S12.Ans.(d)

Sol. If the acceleration due to gravity on the surface of earth is g, then the acceleration due to gravity on the surface of a planet whose mass is same as that of earth and radius is half as that of earth is 4g.

S13.Ans.(d)

Sol. work done = force x distance.

=200×4

=800 joule

S14.Ans.(c)

Sol. Newton’s law of universal gravitation states that every point mass in the universe attracts every other point mass with a force that is directly proportional to the product of their masses, and inversely proportional to the square of the distance between them.

S15.Ans.(a)

Sol. The value of g on earth is maximum at poles and decreases as we go from poles to the equator and is minimum at the equator.

S16. Ans. (d)

Sol. The upward force exerted by the water on the bottle is known as upthrust or buoyant force. In fact, all objects experience a force of buoyancy when they are immersed in a fluid.

S17. Ans.(c)

Sol. The product of force and the time for which the force acts on a body is equal to the change in momentum of the body.

S18. Ans.(d)

Sol.Momentum will be same for object having different masses for the force acting for same amount of time.

S19. Ans.(b)

Sol.If the radius of the earth decreases and its mass remains the same, then the value of “acceleration due to gravity” will increase.

S20. Ans.(b)

Sol.The sensation of weightlessness in a spacecraft in an orbit is due to the acceleration in the orbit which is equal to the acceleration due to gravity outside.

When a spacecraft is in orbit around the Earth, it is in freefall, meaning it is constantly falling towards the Earth but also moving forward at a high enough speed to maintain its altitude and never actually hits the Earth. The acceleration due to gravity and the acceleration of the spacecraft are perfectly balanced, resulting in the sensation of weightlessness for the astronauts inside the spacecraft. Therefore, it is not the absence of gravity, presence of gravity outside but not inside the spacecraft, or lack of energy that causes weightlessness in space.

S21.Ans.(a)

Sol. We know that

Resistance, R =ρ(l/A)

Where ρ is the resistivity, l is the length of wire and A is the cross-sectional area

R = 200×20/100

= 40 ohm.

S22.Ans.(a)

Sol.

H=P X T

=20X2

=40 joule

S23.Ans.(b)

Sol. H = I2Rt

= 0.3 x 0.3 x 900 x 10

= 810 joule

S24. Ans.(d)

Sol. We know that V=IR

R =V/I

=12/0.4

= 120/4

R = 30 Ω

S25. Ans.(b)

Sol. Power =W/T

W=24 x 6

=144 J

S26. Ans.(c)

Sol. Power law equation (formula): P = I × V

=0.1 x 250 =25 W.

S27.Ans(c)

Sol. The heating effect of electric current depends on the resistance (R) of the conductor, the time (t) for which current flows and the amount of current (I).

H = I2Rt

S28. Ans.(a)

Sol. Energy Consumption of 100 watt electric bulb which is used for 10 hours = 100 × 10

= 1000 watt hour

= 1 kilo watt hour

= 1 unit

So, total cost is 1 x 5 = Rs.5

S29.Ans(d)

Sol.

A microwave oven uses microwaves to heat food.
In the case of microwave ovens, the commonly used radio wave frequency is roughly 2,500 megahertz (2.5 gigahertz).
Radio waves in this frequency range absorbed by water, fats, and sugars. When they are absorbed they are converted directly into atomic motion or vibration.
Therefore heavy motion or vibration is converted into heat.

S30. Ans.(a)

Sol. Electric motors operating at low voltage tend to burn out because they draw more current which is inversely proportional to the voltage.

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