STUDENT helper: MID-TERM 1st PU most IMPORTANT question's of physics 2025-2026

Units and Dimensions

The principle of homogeneity of dimensions states that an equation is dimensionally correct if the dimensions of all the terms on both sides of the equation are the same.
Important concepts include applications and limitations of dimensional analysis, and dimensional formulas for quantities like moment of inertia, force, impulse of force, work, and momentum.
A key application is to check the correctness of an equation (e.g., $T = 2 π \sqrt{L / G}$ ) using dimensional analysis.
Derivations include expressing velocity equations using dimensional analysis and deriving expressions for the period of a simple pendulum based on its length and acceleration due to gravity.

Key concepts for two and three-mark questions include deriving expressions like $V = U + A T$ using a velocity-time graph.
Understanding velocity-time graphs for different scenarios is crucial: body at rest, uniform velocity, positive acceleration, negative acceleration, and a freely falling body (decreasing acceleration due to gravity).
Distinctions between speed and velocity, and definitions of average velocity and uniform velocity are important.
Applications of velocity-time graphs in numerical problems involve determining velocity and retardation of a car.

This chapter covers vectors, including unit vectors, and definitions of projectile motion and uniform circular motion.
Understanding dot product and vector product of two vectors is essential.
Important two-mark questions include stating and explaining the triangular law of vector addition and the parallelogram law of vector addition, as well as conditions for vectors to be equal.
Other key concepts are the equation of the trajectory of a projectile (and its nature), and factors influencing centripetal acceleration.
Derivations involve the relationship between linear and angular velocity, expressions for time of flight, maximum height, and horizontal range of a projectile.
Five-mark questions include deriving expressions for centripetal acceleration and finding the magnitude and direction of the resultant of two vectors.
A significant derivation is showing that the trajectory of a projectile is a parabola.

Key topics include impulsive force (which relates to change of momentum) and the laws of friction.
Distinctions between mass and weight of an object, and types of inertia with examples, are important.
Banking of roads (including the outer edge) is a significant concept.
Definitions of angle of friction and angle of repose are also covered.
Five-mark derivations include the equation for the maximum speed of a vehicle on a banked road, stating and proving the law of conservation of linear momentum, and deriving the relation $F = M A$ from Newton's second law.

One and two-mark questions cover definitions of kinetic energy, power, and work done by a force.
Examples of elastic and inelastic collisions are important.
Understanding when work done by a force is positive, negative, or zero, and conditions for maximum/minimum work done.
Concepts include the spring constant of a spring (with its SI unit), types of collision, and what the area under a force-displacement graph represents.
Comparing kinetic energy for heavier vs. lighter bodies with the same momentum is also a question.
Three-mark questions involve stating and proving the work-energy theorem for constant and variable forces, and the difference between conservative and non-conservative forces.
Derivations include expressions for kinetic energy, power ( $P = F \times V$ ), loss of kinetic energy in a one-dimensional inelastic collision, and work done by a variable force.
A five-mark question involves stating and proving the law of conservation of mechanical energy for a freely falling body.
Other five-mark derivations include expressions for the final velocity of a body during an elastic collision and the potential energy stored in an elastic spring using the graphical method.

Definitions include rigid body, torque (in vector form), couple, angular velocity, angular acceleration, moment of inertia (with expression), and radius of gyration (with expression).
Concepts related to the center of mass (its expression and factors it depends on) and the principle of moments (with machine examples) are covered.
Conditions for a rigid body to be in mechanical equilibrium are important.
Three-mark questions include the law of conservation of angular momentum (explained with examples like a diver or ballet dancer) and stating and proving the law of conservation of linear momentum.
Derivations include expressions for torque in terms of angular acceleration and rotational kinetic energy.
A five-mark question requires proving that the rate of change of angular momentum is equal to the torque acting on a body.

This is a very important and easily scorable chapter.
Key topics include stating and explaining Newton's universal law of gravitation, and the relationship between acceleration due to gravity on Earth and the Moon.
Definitions include escape speed, orbital speed of a satellite, gravitational potential energy (with equation and SI unit).
A conceptual question asks why the Moon has no atmosphere.
Three-mark questions include stating and explaining Kepler's laws of planetary motion.
Derivations involve the relation between acceleration due to gravity ( $g$ ) and gravitational constant ( $G$ ), expressions for escape speed, orbital speed, time period, and total energy of a satellite.
Five-mark derivations include expressions for the variation of acceleration due to gravity with respect to height above the Earth's surface and depth below the Earth's surface.
Another five-mark derivation is the expression for gravitational potential energy.

Key topics include stating and explaining Hooke's law and drawing a stress-strain curve with labeled parts (e.g., yield point, fracture point).
Important concepts are the expression for elastic potential energy and mentioning three types of moduli of elasticity (Young's modulus, Shear modulus).
Definitions and SI units for Poisson's ratio and stress modulus of elasticity are also covered.

This chapter covers stating and explaining Bernoulli's principle and its equation, along with three applications of capillarity.
Key concepts include the expression for pressure at a point inside a liquid, and the SI units of viscosity and surface tension.
Understanding the principle behind the uplift of an aeroplane and streamline flow is important.
Pascal's law and its applications (e.g., hydraulic lift) are covered, along with its expression.
The difference between streamline flow and turbulent flow is a key distinction.
Defining the coefficient of viscosity and its expression is also included