Arock of mass m is twirled on a string in a horizontal plane. the work done by the tension in the string on the rock is..

work done by tension force on the twirled stone must be ZERO always

Explanation:

As we know that work done by a force on an object is given as

here we know that

= angle between force and displacement

now we know that tension in the string and displacement of the object is always perpendicular to each other when the rock is twirled in circular path.

so we can say for this motion of the stone

so work done by tension force on the twirled stone must be ZERO always

luster is not a good characteristic to use by itself because luster is the property of minerals that indicates how much the surface of a mineral reflects light. the luster of a mineral is affected by the brilliance of the light used to observe the mineral surface.