Kinetic Energy
Kinetic energy is the energy possessed by a body due to its motion.
In one line: Speed gets squared, so speed matters more.
Practice This ConceptUnderstand it
A moving object can do work because of its motion. Kinetic energy depends on mass and the square of speed. This means doubling mass doubles kinetic energy, but doubling speed makes kinetic energy four times.
Example
Rule to remember
KE = 1/2 mv², where m is mass in kilogram, v is speed in metre per second, and KE is measured in joule.
See it worked out
Follow the example line by line, then use the same method on new questions.
Worked example
For a 4 kg body moving at 3 m/s, KE = 1/2 × 4 × 3² = 2 × 9 = 18 J.
Method you can reuse
Visual tip
A comparison table can show same mass at v and 2v to highlight the square effect of velocity.
Check yourself
Answer the question in your head before opening the answer.
Try it yourself
What happens to kinetic energy if the speed of a body is doubled while mass remains constant?
Think first, then show answerHide answer
Common wrong answer
Forgetting to square velocity gives 1/2 × 4 × 3 = 6 J, which.
Why it loses marks: The formula uses v².
Don't mix this up
Exam tip
Write it in the exam
Each point is worth about one mark. Write point 1 for a 1-mark question and keep adding points as the marks go up.
How CBSE asks it
- 1
Enough for 1 mark
Kinetic energy is the energy possessed by a body due to its motion.
- 2
Add for 2 marks
Example: A moving cricket ball has kinetic energy and can move the stumps when it hits them.
- 3
Add for 3 marks
A moving object can do work because of its motion.
Practice this concept with focused MCQs
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