SI unit of mechanical energy is ____.
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → joule
Mechanical energy (kinetic energy + potential energy) is a form of energy, and the SI unit of all energy and work is the joule (J). One joule is the work done when a force of 1 newton moves a body through 1 metre in the direction of the force.
Why the other options are incorrect
Option (1) newton — Incorrect. The newton is the SI unit of force, not of energy.
Option (2) erg — Incorrect. The erg is the unit of energy in the CGS system; 1 J \(=10^{7}\) erg.
Option (3) dyne-cm — Incorrect. A dyne-centimetre equals one erg, again a CGS unit, not an SI unit.