Final answer:
The seat exerts a normal force of 668.16 N on the student, which is equal in magnitude to the gravitational force acting on the student's mass of 68.18 kg, given no other vertical forces are involved.
Step-by-step explanation:
To answer the question of a high school physics student with a mass of 68.18 kg sitting in a seat and determining the magnitude of the force with which the seat is pushing up upon the student, we use the concept of normal force in physics. The normal force is the force exerted by a surface to support the weight of an object in contact with it and is equal in magnitude and opposite in direction to the force due to gravity (if there are no other forces acting on the object vertically). As the student is at rest and assuming no other vertical forces are involved, the normal force equals the gravitational force acting on the student. This force can be calculated using the equation F = m × g, where F is the force in newtons, m is the mass in kilograms, and g is the acceleration due to gravity (9.80 m/s² on Earth).
Applying the values, we get:
F = 68.18 kg × 9.80 m/s² = 668.16 N.
Therefore, the magnitude of the force is 668.16 N, which corresponds to option C).