A spring of constant 500 N/m is stretched by 0.3 m. How much energy is stored in it?
Answer and explanation
Correct answer: B. 22.5 J
- Step 1: Elastic energy = ½kx². Step 2. E = ½ × 500 × 0.3² = 22.5 J. Answer: 22.5 J. Why not the others: 45 J is what you get if you forget the factor ½. 75 J is what you get if you forget to square the extension. 150 J is what you get if you give the force instead.
Practise more Electricity, Magnetism and Modern Physics.
Free questions with an explanation for every one, and full timed ECAT Pakistan mock tests.
More Electricity, Magnetism and Modern Physics questions
- A body moves in a circle of radius 10 m at 30 m/s. What is its centripetal acceleration?
- A body slides down a smooth slope at an angle whose sine is 4/5. What is its acceleration? (take g = 10 m/s²)
- A 40 kg load hangs 2 m from the pivot of a light uniform lever. What force at 0.5 m on the other side of the pivot balances it? (take g = 10…
- A body of volume 0.002 m³ is fully immersed in a liquid of density 1200 kg/m³. What is the upthrust? (take g = 10 m/s²)
- A 5 kg trolley moving at 6 m/s hits a stationary 1 kg trolley and they stick together. What is their common speed?
- A body moving at 4 m/s accelerates uniformly at 8 m/s² for 8 s. What is its final speed?