Question

A boy pulls a 5 kg block 20m along a horizontal surface at a constant speed with a force directd 45°
horizontal. If the coefficient of kinetic friction is 0.2. how much work does the boy do on the block ​

Answer 1

ANSWER...

$mass = 5kg \\ \\ displacement = 20m \\ \\ \alpha = 45 \\ \\ ACCELERATION = 0 \\ because \: it \: is \: mentioned \: that \: the \: \\ body \: travels \: with \: constant \: speed \\ and \: we \: know \: that \: if \: spe<strong>e</strong>d \: is \: constant \: \\ than \: magnitude \: of \: velocity \: is \\ also \: constant \: hence \: change \: in \: \\ velocity \: is \: zero \: \\ hence \: ACCELERATION \ : is \: \\ zero \\ \\ force = mass \times acceleration \\ \\ work = force \times displacement \times \cos \alpha \\ \\ work \: done \: is \: zero$

THE POINT TO BE NOTED THAT WORK DONE BY THE BOY IS ZERO

BUT THE WORK IS DONE ON THE BODY DUE TO FRICTIONAL FORCE BUT BY THE BOY IT IS EQUAL TO ZERO