Calculate work of a man holding a barbell at chest hight 2 m for 15 seconds?

Answer: 0J

The equation for work is W=Fdcos (x), where w=work, f=force, d=displacement, and x=angle the force makes with the displacement vector.

Since the man is holding a barbell and the object, the barbell, isn't being displaced, d=0, making the work done equal to zero.