Final answer:
The football will hit the ground at a 40° angle, which is the same as the launch angle due to the symmetry of projectile motion when air resistance is ignored.
Step-by-step explanation:
A place kicker kicks a football at an angle of 40°. At what angle will the ball hit the ground? The correct answer is that the ball will hit the ground at the same angle it was launched if we ignore air resistance and other external factors, due to the symmetry of projectile motion (angle of incidence equals angle of reflection). Therefore, the ball will hit the ground at a 40° angle, making option a. 40° the correct choice. In projectile motion, the angle of launch determines the trajectory of the object. As the launch angle increases, the trajectory becomes more parabolic, reaching its peak at 45° for maximum horizontal distance (optimum angle of projection). Angles beyond this will result in a steeper ascent and descent. However, at any angle of launch, when neglecting air resistance, the angle at which the projectile lands will be the same as the launch angle.