Question

A man pulls a block of mass $m$ along the horizontal track with kinetic friction $\mu$ using a rope which makes an angle $\theta$ with the horizontal as shown in the figure. The block moves with constant speed $v$. Power delivered by man is

• A. $Tv$
• B. $Tv\cos \theta$
• C. $(T\cos \theta -\mu mg)v$
• D. Zero

Answer 1

The correct option is B $Tv\cos \theta$

Given that block slides along the track with kinetic friction ${}^{\prime }{\mu }^{\prime }$ with a constant speed ${}^{\prime }{v}^{\prime }$.

As friction only opposes the relative motion between two bodies power delivered by man

Here the force applied by the man is $T$, $(F=T)$

We know that, $\left(P\right)=F.v=Fv\cos \theta =Tv\cos \theta$.

Hence option B is the correct answer