Correct Answer - Option 4 : 2 times

__Concept:__

Power is given by;

__\(% MathType!Translator!2!1!AMS LaTeX.tdl!AMSLaTeX! % MathType!MTEF!2!1!+- % feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaaeaaaaaaaaa8 % qacaWGqbGaeyypa0ZaaSaaa8aabaWdbiaaikdacqaHapaCcaWGobGa % amivaaWdaeaapeGaaGOnaiaaicdaaaaaaa!3DDF! P = \frac{{2π NT}}{{60}}\)\(P = \frac{{2\pi NT}}{{60}}\)__

Where P is in watt

N = Angular velocity

T = Torque

__Calculation:__

Given,

T' = 2T

\(P \propto T\)

\(\frac{{P'}}{P} = \frac{{T'}}{T} = \frac{{2T}}{T}\) ⇒** P' = 2P**

So, If the horse power of a shaft subjected to **torque alone is doubled**, **horse power can be increased 2 times.**