Question 1 - A-Level Maths

A golf ball and a table tennis ball are dropped together from the top of a building. The golf ball hits the ground after 1.7 seconds.
1. Calculate the height of the top of the building above the ground.
According to a simple model, the two balls hit the ground at the same time.
State why this may not be true in practice and describe a refinement to the model which could lead to a more realistic solution.