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., $T=2\pi \sqrt{L\mathrm{/}G}$) 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. 

Motion in a Straight Line

• Key concepts for two and three-mark questions include deriving expressions like $V=U+AT$ 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. 

Motion in a Plane

• 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. 

Laws of Motion

• 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 $F=MA$ from Newton's second law. 

Work, Energy, and Power

• 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. 

System of Particles

• 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. 

Gravitation

• 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. 

Mechanical Properties of Solids

• 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. 

Mechanical Properties of Fluids

• 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