Question

A train that weighs 1,000,000KG is moving at a stable speed of 20m/s with a force of friction that equals 20,000N.

Q: Find the power of the train's locomotive.

Answer 1

The Newton’s second law states
ma=F_(trein locomotive)-F_friction=0
Since a train moves with a stable speed, the acceleration a is zero. So
F_(trein locomotive)=F_friction=20 000 N
The power of the train's locomotive
P=(work done)/time=(F_(trein locomotive)×distance)/time=F_friction×speed
=20 000 N×20 m/s=400 000 W=400 kW