Here's how to calculate the force the pitcher exerts on the baseball:

1. Convert mass to kilograms:

* 250 grams = 0.25 kilograms (since 1 kg = 1000 g)

2. Use Newton's Second Law of Motion:

* Force (F) = Mass (m) x Acceleration (a)

3. Plug in the values:

* F = 0.25 kg * 50 m/s²

* F = 12.5 Newtons

Therefore, the pitcher exerts a force of 12.5 Newtons on the baseball.