AimMent

For Class 8, 9 & 10

Foundation - a strong base in Physics, Chemistry, Maths & Biology

Concept-first questions with clear model answers across all four subjects, aligned to NCERT. Start early, build the habit, and walk into your board exams, NEET and JEE already ahead.

Class 824Class 924Class 1036
SubjectAllPhysics 19Chemistry 19Biology 19Mathematics 27
ChapterAllAlgebraic Expressions and IdentitiesCell Structure and FunctionsChemical Effects of Electric CurrentCoal and PetroleumCombustion and FlameComparing QuantitiesConservation of Plants and AnimalsCrop Production and ManagementExponents and PowersForce and PressureFrictionLightLinear Equations in One VariableMaterials: Metals and Non-MetalsMensurationMicroorganisms: Friend and FoePollution of Air and WaterReaching the Age of AdolescenceReproduction in AnimalsSome Natural PhenomenaSoundSquares and Square RootsSynthetic Fibres and Plastics

Showing 1 question for Class 8. Tap a card to reveal the answer.

PhysicsFrictionmedium

Why is friction called a necessary evil?

Reveal answer ↓

What it is

Friction is the grip between two surfaces that resists sliding.

Answer

Friction is called a necessary evil because it is both useful and harmful. It is necessary as it lets us walk, hold objects, write and stop vehicles. It is an evil because it wears out machine parts and shoe soles and produces heat that wastes energy. So we increase it where needed (treads, brakes) and reduce it where it wastes energy (lubricants, ball bearings).

  • •Useful: walking, gripping, braking, writing
  • •Harmful: wear and tear, heat, energy loss
  • •Increase with treads/brakes; reduce with lubricants/ball bearings

Why learn this

Without it you couldn't walk, write or brake; too much of it wastes fuel and wears parts out.

💡 Memory trick

Friction is a Friend that also causes Fiction (trouble).