Final answer:
The weight of a 15 kg backpack is 147 Newtons, and the mass of a barbell that weighs 392 N is 40 kg. These values are calculated using the relationship between mass, weight, and gravitational acceleration.
Step-by-step explanation:
Determining Weight and Mass
To determine the weight of a 15 kg backpack, we use the formula Weight (W) = Mass (m) × Gravitational Acceleration (g), where g is approximately 9.8 m/s² on Earth. Therefore, for a mass of 15 kg, the weight W = 15 kg × 9.8 m/s², which equals 147 Newtons (N).
To determine the mass of a barbell with a weight of 392 N, we use the rearranged formula Mass (m) = Weight (W) / Gravitational Acceleration (g). Thus, the mass m = 392 N / 9.8 m/s², which gives us a mass of 40 kg.
These calculations are examples of how to determine the weight of a person or the weight of a bag of sand, as well as how to estimate physical quantities related to lifting, such as the mass of a barbell during a weigh-in for a sports team or the power exerted by a weightlifter.