Response:
The normal force acting on the ant is 0.75 N.
Explanation:
Provided;
the diameter of the ball, D = 40 cm = 0.4 m
radius of the ball, r = 0.2 m
weight of the beach ball, m₁ = 300 g = 0.3 kg
weight of the ant, m₂ = 4 x 10⁻⁶ kg
velocity of the ball, v = 4 m/s
The area of a spherical ball is given by;
A = 4πr²
A = 4π(0.2)² = 0.5027 m²
The drag force (resistance) encountered by the spherical ball is given as;

where;
C is the drag coefficient of the spherical ball = 0.45
ρ is the air density = 1.21 kg/m³

The downward force from the ball caused by its weight and that of the ant is given by;

The resultant downward force acting on the ball is given by;

This downward force is equal to the normal reaction it applies to the ant.
Consequently, the normal force impacting the ant is 0.75 N.