A10-kg rock and a 20-kg rock are thrown upward with the same initial speed v0 and experience no significant air resistance. if the 10-kg rock reaches a maximum height h, what maximum height will the 20-kg ball reach?

At maximum height, initial velocity

Here, h is maximum height and g is acceleration due to gravity.

According to above relation, the vertical height does not depend on the mass of body it depend only upon the initial velocity.

Therefore, the 20 kg rock reach the same height as 10 kg rock.