The acceleration due to gravity is 9.8 m/s, assuming the boy is on Earth. You multiply 4 seconds by 9.8, which equals about 39 m/s. The boy doesn’t add any force, so only gravity acts on the ball. You don’t need distance because time is given. You can find the distance if you need to use the formula d=1/2at^2, since the initial velocity is zero, “a” being the acceleration, in this case the acceleration due to gravity, and “t” being the time.