Question

A sphere of mass M tied to the end of a string of length L moves along a horizontal circular path with constant speed V .The work done in a complete circle is :
a)zero
b)mv2/L*2pie L
c)mg.2pie L
d)mv2/L *L​

Answer 1

Answer:

option(a)=0

Explanation:

As it is of mass " m" and makes a complete cirlce,

its work done will be "0"

why?

because,

W=F.S.cos(@)

and if the circle comes to the same place where ut was relaesed then displacement is 0, so there work done will be 0 no matter hownmany rounds did it covered!!

thanksn

Answer 2

Method - 1:

Work done by centripetal force in uniform circular motion is always equal to zero.

Therefore, Work done in a complete circle is Zero.

Method - 2:

The velocity of the bob at the extreme position is Zero, so momentum transferred to the ball is also Zero.

Therefore, Work done in a complete circle is Zero.

Method - 3:

The Work done is defined by W = F * D, where F denotes Force and  D denotes displacement, * denotes cross product.

In case of uniform circular motion(speed v constant) the centripetal force( here provided by tension in the string) is the only force acting on the body and is passing through the center of the circle and f is taken from the same center the cross product F * D=0. The work done is zero.

Therefore, Work done is Zero.

Hope this information helps!