Final answer:
The weight of a high school student with a mass of 70 kg is found by multiplying the mass by the acceleration due to gravity (9.8 m/s^2), resulting in a weight of 686 N.
Step-by-step explanation:
The weight of an object is calculated by multiplying its mass by the acceleration due to gravity, which is approximately 9.8 m/s2 on Earth. For a high school student with a mass of 70 kg, the weight would be:
Weight (W) = mass (m) × acceleration due to gravity (g)
W = 70 kg × 9.8 m/s2
W = 686 N
Therefore, the correct answer is b) 686 N.