NEET 2015 Physics PYQs: Questions Every NEET Aspirant Must Master
Learn the Question. Understand the Formula. Master the Concept.
Physics in NEET is not about memorising hundreds of formulas. The real key to scoring well is understanding which concept to apply, when to apply it and how to solve a problem step by step.
Previous Year Questions are one of the best ways to understand the level and pattern of questions asked in NEET. The NEET 2015 Physics paper tested important concepts from topics such as Gravitation, Thermodynamics, Units and Measurements, Circular Motion, Work, Energy and Power and Rotational Motion.
In this blog, Pentagon Institute explains selected NEET 2015 Physics PYQs in a simple and student-friendly format.
For every question, you will learn:
Question
Correct Answer
Step-by-Step Solution
Core Concept
Easy Example
Quick Revision Tip
1. Satellite in an Elliptical Orbit – Where Is Its Acceleration Directed?
Question
A satellite is moving around the Earth in an elliptical orbit. Which statement is correct?
Correct Answer
The acceleration of the satellite is always directed towards the centre of the Earth.
Chapter
Gravitation
Detailed Solution
A satellite moves around the Earth because of gravitational force.
The gravitational force exerted by the Earth always acts towards the centre of the Earth.
According to Newton's Second Law:
F = ma
The acceleration of an object acts in the direction of the net force.
Therefore:
Gravitational Force → Towards the centre of the Earth
Acceleration → Towards the centre of the Earth
Hence, the acceleration of the satellite is always directed towards the centre of the Earth.
Core Concept
Gravity is a central force.
A central force acts along the line joining two bodies. In the case of a satellite:
Earth → Satellite
Since gravitational force is a central force, the torque about the centre of the Earth is zero.
Therefore:
Angular Momentum is Conserved
If only gravitational force acts, the total mechanical energy of the satellite also remains constant.
However, the satellite's speed changes as its distance from the Earth changes.
Example
When a satellite moves closer to the Earth:
Distance decreases → Speed increases
When a satellite moves farther away:
Distance increases → Speed decreases
NEET Quick Tip
Central Force → Zero Torque → Angular Momentum Conserved
2. Degrees of Freedom – Finding Gamma
Question
If the degree of freedom of an ideal gas is f, find:
γ = Cp/Cv
Correct Answer
γ = 1 + 2/f
Chapter
Thermodynamics and Kinetic Theory of Gases
Step-by-Step Solution
For an ideal gas:
Cv = fR/2
We also know:
Cp = Cv + R
Substituting:
Cp = fR/2 + R
Now:
γ = Cp/Cv
Therefore:
γ = (fR/2 + R)/(fR/2)
After simplification:
γ = 1 + 2/f
Core Concept
The value of gamma depends on the number of degrees of freedom of a gas molecule.
More degrees of freedom mean more ways in which a molecule can store energy.
Example 1: Monoatomic Gas
For a monoatomic gas:
f = 3
Therefore:
γ = 1 + 2/3 = 5/3
Example 2: Diatomic Gas
For a diatomic gas:
f = 5
Therefore:
γ = 1 + 2/5 = 7/5
Quick Revision
Monoatomic Gas → γ = 5/3
Diatomic Gas → γ = 7/5
NEET Quick Tip
Questions related to Cp, Cv, Degrees of Freedom and Gamma are frequently interconnected.
Learn the formula along with the concept.
3. Units and Dimensions – Surface Tension
Question
If Energy (E), Velocity (V) and Time (T) are taken as fundamental quantities, find the dimensions of Surface Tension.
Correct Answer
[EV⁻²T⁻²]
Chapter
Units and Measurements
Step-by-Step Solution
Surface tension is defined as:
Surface Tension = Force / Length
The dimensional formula of force is:
[MLT⁻²]
Therefore:
Surface Tension = [MLT⁻²]/[L]
So:
Surface Tension = [MT⁻²]
Now assume:
Surface Tension = EˣVʸTᶻ
We know:
Energy = [ML²T⁻²]
Velocity = [LT⁻¹]
By comparing the dimensions of both sides, we get:
x = 1
y = -2
z = -2
Therefore:
Surface Tension = EV⁻²T⁻²
Core Concept
Dimensional analysis is based on a simple rule:
The dimensions on both sides of a physically correct equation must be the same.
Example
Consider:
s = ut + ½at²
Dimensions of displacement:
s = Length
Dimensions of:
ut = (LT⁻¹)(T) = L
Dimensions of:
at² = (LT⁻²)(T²) = L
All terms have the dimensions of length.
Therefore, the equation is dimensionally correct.
NEET Quick Tip
For dimensional analysis:
Required Quantity → Write Dimensions → Compare Powers → Solve
4. Circular Motion – Finding Speed from a Position Vector
Question
The position vector of a particle is:
R = 4sin(2πt)i + 4cos(2πt)j
Find the speed of the particle.
Correct Answer
Speed = 8π m/s
Chapter
Motion in a Plane and Circular Motion
Step-by-Step Solution
The coordinates are:
x = 4sin(2πt)
y = 4cos(2πt)
Squaring and adding:
x² + y² = 16sin²(2πt) + 16cos²(2πt)
Using:
sin²θ + cos²θ = 1
We get:
x² + y² = 16
This represents a circle.
Therefore:
Radius = 4 m
Now differentiate the position vector:
v = dR/dt
Therefore:
v = 8πcos(2πt)i - 8πsin(2πt)j
The magnitude of velocity is:
|v| = √[(8πcos)² + (8πsin)²]
Using:
sin²θ + cos²θ = 1
Therefore:
Speed = 8π m/s
Core Concept
If:
x = Rcosωt
and:
y = Rsinωt
the particle performs Uniform Circular Motion.
The formula is:
v = Rω
Example
If:
Radius = 2 m
Angular Velocity = 5 rad/s
Then:
v = Rω
v = 2 × 5
v = 10 m/s
NEET Quick Tip
Whenever you see sine and cosine in the position vector, first check:
x² + y²
It may immediately reveal circular motion.
5. Constant Power – How Does Force Change?
Question
A particle of mass m starts from rest.
A machine supplies constant power:
P = k
Find the force acting on the particle after time t.
Correct Answer
F = √(mk/2t)
Chapter
Work, Energy and Power
Step-by-Step Solution
Power is:
Power = Work/Time
Given:
P = k
Therefore:
Work Done = kt
According to the Work-Energy Theorem:
Work Done = Change in Kinetic Energy
Since the particle starts from rest:
kt = ½mv²
Therefore:
v² = 2kt/m
Taking square root:
v = √(2kt/m)
We also know:
P = Fv
Therefore:
F = P/v
Substituting:
F = k/√(2kt/m)
After simplification:
F = √(mk/2t)
Core Concept
For constant power:
P = Fv
Therefore:
F ∝ 1/v
As velocity increases, force decreases.
Example
Imagine a machine supplying constant power.
Initially:
Velocity is low → Force is high
Later:
Velocity increases → Force decreases
NEET Quick Tip
Constant Power does not mean Constant Force.
This is an important conceptual difference.
6. Conservation of Angular Momentum – What Happens When Radius Decreases?
Question
A particle of mass m moves in a circular path of radius R₀ with velocity v₀.
The radius is gradually reduced to:
R₀/2
Find the final kinetic energy.
Correct Answer
Final Kinetic Energy = 2mv₀²
Chapter
System of Particles and Rotational Motion
Step-by-Step Solution
The force due to the string acts towards the centre.
Therefore, the external torque about the centre is zero.
Hence:
Angular Momentum is Conserved
Initial angular momentum:
Li = mv₀R₀
Final radius:
R = R₀/2
Final angular momentum:
Lf = mv(R₀/2)
According to conservation of angular momentum:
Li = Lf
Therefore:
mv₀R₀ = mv(R₀/2)
Cancelling common terms:
v = 2v₀
Now:
Kinetic Energy = ½mv²
Therefore:
Kf = ½m(2v₀)²
Kf = 2mv₀²
Core Concept
When external torque is zero:
Angular Momentum is Conserved
For a particle:
mvr = Constant
Therefore:
v ∝ 1/r
If the radius becomes half:
Velocity becomes double
Example
A skater spins faster when they pull their arms closer to their body.
This happens because of the conservation of angular momentum.
NEET Quick Tip
Whenever you see:
Radius changes + No External Torque
Think immediately:
Conservation of Angular Momentum
What Should You Learn from NEET Physics PYQs?
Every Previous Year Question should teach more than just one answer.
For example:
Question → Satellite Motion
Do not only remember:
Answer → Acceleration is towards the Earth
Also understand:
Chapter → Gravitation
Concept → Central Force
Related Topic → Torque
Result → Angular Momentum Conservation
This is how one question can help you revise multiple connected concepts.
The Smart PYQ Method for NEET Physics
Step 1: Identify the Chapter
Ask yourself:
Which chapter does this question belong to?
Step 2: Identify the Core Concept
Ask:
What physical principle is being tested?
Step 3: Select the Correct Formula
Before using a formula, understand why that formula is applicable.
Step 4: Solve Step by Step
Follow:
Given → Concept → Formula → Calculation → Answer
Step 5: Analyse Mistakes
If your answer is incorrect, identify the reason:
Wrong concept
Wrong formula
Calculation mistake
Unit conversion error
Misreading the question
Pentagon Institute's Smart NEET Physics Learning Formula
Learn the Concept
↓
Understand the Formula
↓
Identify the Physical Principle
↓
Solve Step by Step
↓
Practice MCQs
↓
Analyse PYQs
↓
Correct Mistakes
↓
Revise Again
Final Takeaway
The best NEET Physics students do not simply memorise formulas.
They understand:
Which chapter the question belongs to
What concept is being tested
Which formula should be applied
Why the solution works
Where the same concept can be applied again
So, do not study Previous Year Questions simply as:
Question → Answer
Study them as:
Question → Chapter → Concept → Formula → Solution → Example → Revision
With regular concept revision, formula practice, PYQ analysis and consistent problem-solving, Physics can become one of your strongest scoring subjects in NEET.
Frequently Asked Questions
Are NEET 2015 Physics PYQs useful for current NEET preparation?
Yes. Previous Year Questions are useful for understanding important concepts, question patterns and the level of application required in NEET Physics.
Should I memorise Physics PYQ solutions?
No. Always understand:
The concept
The formula
The solution steps
The reason behind the answer
Which chapters should I revise after solving these PYQs?
Focus on:
Gravitation
Work, Energy and Power
Circular Motion
Rotational Motion
Thermodynamics
Kinetic Theory of Gases
Units and Measurements
How can I improve my NEET Physics score?
Follow this approach:
Learn Concept → Understand Formula → Solve Basic Questions → Practice MCQs → Analyse PYQs → Revise Mistakes
Great