Final answer:
The question pertains to physics and involves calculating the trajectory of a tennis serve as well as the force of impact from a famous serve by Venus Williams.
Step-by-step explanation:
Calculating Projectile Motion in Tennis
When a tennis player serves a ball at a speed of 170 km/h and at a specific angle below the horizontal, we are dealing with physics, specifically projectile motion. To calculate the angle at which the ball just crosses the net and whether it will land in the service box, we need to consider the initial conditions of the serve, the dimensions of the court, and the laws of motion. The angle must be such that the vertical distance to the net (0.91m) is cleared, but the ball must also drop within the service box, 6.40m from the net. Using the given parameters and projectile motion equations, one can solve for the required angle.
For Venus Williams' serve during the 2007 French Open, where she hit the ball at a speed of 58 m/s, we are interested in calculating the average force exerted on the ball by her racquet. Given the mass of the ball (0.057 kg) and the time of contact with the racquet (5 ms), we can use the impulse-momentum theorem to determine the average force.