When a ball is thrown upward, its speed decreases due to the opposing force of gravity until it reaches its highest point. At that point, its speed becomes zero before it starts falling back down.
To determine the speed of the ball when it returns to the starting point, we can use the concept of conservation of energy. The initial kinetic energy of the ball when it was thrown upward is converted into potential energy at the highest point, and then it is converted back to kinetic energy as the ball falls.
At the starting point, the ball will have the same speed as it had when it was thrown upward, but in the opposite direction. So, the speed when it returns to the starting point will also be 5 m/s.
Therefore, the speed of the ball when it returns to the starting point will be 5 m/s.