Question

why is the work done on an object moving with uniform circular motion zero ?

Answer 1

Work= force ×displacement
In uniform circular motion total displacement is zero since direction changes frequently
Since displacement becomes zero the work is also zero because zero multiplied by any number is zero.

Answer 2

Work done = force x displacement
=f x s
=(m x a) x s
Since the acceleration is zero,
Hence
Work done = (m x 0) x s
=0

Hope this helped you