Force, Motion and Work

Overview

Force, Motion and Work form the backbone of classical mechanics and are essential topics for TN TET Paper II (Mathematics and Science). This unit tests your understanding of how objects move, what causes them to move or stop, and how energy is transferred through work. Questions typically involve definitions, laws of motion, numerical problems on work-energy, and identification of simple machines.

For TN TET, expect 3-5 questions from this area. You must be comfortable with Newton's laws, types of friction, calculation of work and energy, mechanical advantage of simple machines, and real-life applications. Conceptual clarity matters more than complex calculations at this level.

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Key Concepts

• **Force** is a push or pull that can change an object's state of rest or motion, its shape, or its direction. SI unit: Newton (N). Force is a vector quantity (has magnitude and direction).

• **Inertia** is the tendency of an object to resist change in its state of motion. Mass is the measure of inertia—greater mass means greater inertia.

• **Friction** is the force that opposes relative motion between two surfaces in contact. It depends on the nature of surfaces and normal force, not on area of contact.

• **Motion** is the change in position of an object with respect to time and a reference point. Types include rectilinear (straight line), circular, oscillatory and random motion.

• **Work** is done when a force causes displacement in its direction. Work = Force × Displacement × cos θ. No displacement means no work done.

• **Energy** is the capacity to do work. It exists in many forms—kinetic, potential, heat, light, sound, chemical, electrical.

• **Simple machines** make work easier by multiplying force, changing direction of force, or increasing speed. They do not reduce the total work done.

• **Mechanical Advantage (MA)** = Load / Effort. It tells how many times a machine multiplies the effort force.

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Formulas / Key Facts

| Quantity | Formula | Unit | |----------|---------|------| | Force | F = m × a | Newton (N) | | Weight | W = m × g (g ≈ 10 m/s²) | Newton (N) | | Work | W = F × d × cos θ | Joule (J) | | Kinetic Energy | KE = ½ × m × v² | Joule (J) | | Potential Energy | PE = m × g × h | Joule (J) | | Power | P = Work / Time = W / t | Watt (W) | | Mechanical Advantage | MA = Load / Effort | No unit | | Velocity Ratio | VR = Distance moved by effort / Distance moved by load | No unit | | Efficiency | η = (MA / VR) × 100% | Percentage |