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.
Showing 1 question in Physics for Class 9. Tap a card to reveal the answer.
PhysicsWork and EnergymediumDefine work done by a force and state the formula for kinetic energy.
Reveal answer ↓
What it is
Work is force times the distance moved along it; a moving object stores that work as kinetic energy.
Answer
Work is done when a force acts on a body and the body moves in the direction of the force; work done W = F s cos(theta), where s is the displacement and theta is the angle between the force and the displacement. Kinetic energy is the energy possessed by a body due to its motion and is given by KE = (1/2) m v^2. The unit of both work and energy is the joule.
W = F s cos(theta) ; KE = (1/2) m v^2
- •Work needs force and displacement along it
- •W = F s cos(theta)
- •Kinetic energy KE = (1/2) m v^2
- •Unit is the joule (J)
Why learn this
It underlies electricity bills (energy) and how a dam, a bow-and-arrow or a moving car works.
💡 Memory trick
No movement, no work. KE = 1/2 m v^2 - double the speed, FOUR times the energy.