IIT JEE Physics Practice Paper – SET 1 Mechanics

Solve 30 IIT JEE Physics Mechanics questions with answers, explanations, and instant scoring.

Attempt all 30 questions. Each carries 4 marks. No negative marking.

Q1. A particle moves with constant acceleration. Ratio of velocities in 1s and 2s?

1 : 2
1 : 4
2 : 1
4 : 1

Q2. Work done by gravity in a closed path is:

Zero
Positive
Negative
Infinite

Q3. Dimensions of force are:

MLT⁻²
ML²T⁻²
M²LT⁻²
ML⁻¹T⁻²

Q4. Angle for maximum range of projectile is:

45°
30°
60°
90°

Q5. Kinetic energy is proportional to:

v
v²
v³
1/v

Q6. Acceleration at highest point of projectile:

0
g
2g
-g

Q7. SI unit of momentum:

kg·m/s
Newton
Joule
Watt

Q8. If net force on body is zero, motion is:

Rest
Uniform motion
Accelerated
Random

Q9. Escape velocity depends on:

Mass
Radius
Both mass and radius
None

Q10. Work-energy theorem relates:

Force
Work & kinetic energy
Momentum
Velocity

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IIT JEE Physics Notes – Mechanics (Practice Paper Part 1)

Mechanics forms the backbone of IIT JEE Physics, and this quiz covers several fundamental concepts that every aspirant must master. These notes consolidate the key ideas, formulas, and conceptual clarity required to solve such questions effectively.

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1. Kinematics and Motion Basics

In problems involving constant acceleration, velocity changes linearly with time. The key equations are:

• $v = u + at$v=u+at
• $s = ut + \frac{1}{2}at^2$s=ut+21​at2
• $v^2 = u^2 + 2as$v2=u2+2as

If a particle starts from rest, velocity becomes directly proportional to time ($v \propto t$v∝t). That’s why velocity ratios often reduce to time ratios.

Graphs are extremely important:

• Slope of velocity-time graph = acceleration
• Area under velocity-time graph = displacement
• Area under acceleration-time graph = change in velocity

Understanding graphical interpretation is crucial for JEE.

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2. Projectile Motion

Projectile motion is a combination of horizontal and vertical motion:

• Horizontal velocity remains constant
• Vertical motion has acceleration = $g$g

Key formulas:

• Time of flight: $T = \frac{2u \sin\theta}{g}$T=g2usinθ​
• Range: $R = \frac{u^2 \sin 2\theta}{g}$R=gu2sin2θ​
• Maximum height: $H = \frac{u^2 \sin^2\theta}{2g}$H=2gu2sin2θ​

Maximum range occurs at $45^\circ$45∘.
At the highest point, velocity is horizontal but acceleration is still $g$g downward — a very common conceptual trap.

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3. Newton’s Laws of Motion

Newton’s laws define how forces affect motion:

• First Law: A body remains at rest or uniform motion if net force is zero
• Second Law: $F = ma$F=ma
• Third Law: Action = Reaction

If net force is zero, acceleration is zero — but velocity may not be zero. This means the object can still move with constant velocity.

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4. Work, Energy, and Power

Work is defined as:$$W = F \cdot s \cdot \cos\theta$$W=F⋅s⋅cosθ

Important cases:

• $\theta = 0^\circ$θ=0∘ → Maximum work
• $\theta = 90^\circ$θ=90∘ → Work = 0
• $\theta = 180^\circ$θ=180∘ → Negative work

Kinetic Energy:$$KE = \frac{1}{2}mv^2$$KE=21​mv2

Potential Energy:$$PE = mgh$$PE=mgh

Work-Energy Theorem:$$W = \Delta KE$$W=ΔKE

Power:$$P = \frac{W}{t}$$P=tW​

These formulas are frequently used in JEE problems involving motion and forces.

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5. Momentum and Impulse

Momentum is defined as:$$p = mv$$p=mv

Impulse:$$Impulse = F \times t = \Delta p$$Impulse=F×t=Δp

This concept is important in collision problems. If a large force acts for a short time, it can still produce significant change in momentum.

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6. Collisions

There are two main types:

• Elastic Collision:
  • Momentum conserved
  • Kinetic Energy conserved
• Inelastic Collision:
  • Momentum conserved
  • KE not conserved

Perfectly inelastic collisions involve objects sticking together.

Understanding conservation laws is key for solving collision-based numerical problems.

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7. Circular Motion

For a body moving in a circle:

Centripetal force:$$F = \frac{mv^2}{r}$$F=rmv2​

Direction: Always towards the center.

Angular velocity:$$\omega = \frac{v}{r}$$ω=rv​

Unit: rad/s

Important insight: Even if speed is constant, velocity changes due to direction — hence acceleration exists.

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8. Gravitation

Gravitational force:$$F = \frac{GMm}{r^2}$$F=r2GMm​

Acceleration due to gravity:$$g = \frac{GM}{R^2}$$g=R2GM​

If radius increases, gravity decreases (inverse square relationship).

Escape velocity:$$v_e = \sqrt{\frac{2GM}{R}}$$ve​=R2GM​​

It depends on both mass and radius of the planet.

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9. Friction

Frictional force:$$f = \mu N$$f=μN

Depends on:

• Nature of surfaces
• Normal reaction

It does NOT depend on surface area directly.

Types:

• Static friction
• Kinetic friction

Static friction adjusts itself up to a maximum value.

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10. Elasticity and Hooke’s Law

Hooke’s Law:$$F = kx$$F=kx

Valid only within elastic limit.

Beyond elastic limit, permanent deformation occurs and the law is no longer valid.

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11. Rotational Mechanics

Torque:$$\tau = r \times F$$τ=r×F

Angular momentum:$$L = r \times p$$L=r×p

Conservation of angular momentum occurs when no external torque acts.

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12. Important Conceptual Insights

• Work done by conservative forces (like gravity) in a closed loop is zero
• Acceleration due to gravity is always downward near Earth
• Kinetic energy depends on square of velocity
• If KE remains constant and mass increases, velocity must decrease
• Negative work occurs when force opposes displacement

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13. Dimensional Analysis

Used to check correctness of equations.

Example:
Force:$$[F] = MLT^{-2}$$[F]=MLT−2

Energy:$$[ML^2T^{-2}]$$[ML2T−2]

This helps eliminate wrong options in MCQs.

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Final Strategy for IIT JEE

• Focus on concept clarity, not just formulas
• Practice mixed concept questions
• Use dimensional analysis to eliminate options
• Revise formulas daily
• Solve previous year questions

Mechanics questions in JEE often combine multiple concepts (e.g., energy + motion + force), so integrated understanding is essential.