Question

a dynamo of an engine rotates at 2800 rev/min, through how many radians does it turns in 90sec.?

Answer 1

In one minute the dynamo rotates 2800 times

⇒ in one second the dynamo rotates 2800/60 times ⇒ that is 140/3 times

we know that 1rev = 2π radians

⇒ in one second the dynamo turns 280π/3 radians = 293.2 radians

⇒ if in one second the dynamo turns 293.2 radians

⇒ in 90 seconds the dynamo turns (293.2 × 90)radians = 26389 radians