Final answer:
The force exerted on the ground by a 65 kg football player because of gravity is calculated as 650 N when using the approximate value of 10 m/s² for the acceleration due to gravity.
Step-by-step explanation:
The force that a 65 kg football player exerts on the ground due to gravity can be calculated using the formula for weight, F = m × g, where F is the force in Newtons, m is the mass in kilograms, and g is the acceleration due to gravity, which is approximately 9.8 m/s² on Earth. Using the football player's mass of 65 kg:
F = 65 kg × 9.8 m/s² = 637 N
However, we typically round the gravitational acceleration to 10 m/s² for simple calculations, which yields:
F = 65 kg × 10 m/s² = 650 N
Therefore, the correct answer is a) 650 N.