What is the kinetic energy of a 5 kg body moving at 15 m/s?
Answer and explanation
Correct answer: C. 562.5 J
- Step 1: KE = ½mv². Step 2. KE = ½ × 5 × 15² = 562.5 J. Answer: 562.5 J. Why not the others: 1125 J is what you get if you forget the factor ½. 37.5 J is what you get if you forget to square the speed. 281.25 J is what you get if you halve twice.
Practise more Mechanics, waves and electricity.
Free questions with an explanation for every one, and full timed WBJEE mock tests.
More Mechanics, waves and electricity questions
- What force gives a mass of 9 kg an acceleration of 9 m/s²?
- What is the kinetic energy of a 20 kg body moving at 4 m/s?
- How much gravitational potential energy does a 2 kg mass gain when lifted 11 m? (take g = 10 m/s²)
- A machine takes in 800 J of energy and gives out 600 J of useful work. What is its efficiency?
- What is the pressure due to a column of liquid of density 800 kg/m³ and depth 10 m? (take g = 10 m/s²)
- A resistor of 2 Ω carries a current of 5 A. What is the potential difference across it?