Final answer:
The change in Mary's potential energy is calculated using the formula PE = mgh, resulting in 1656.6 joules. Mary's weight is given as 502 newtons, which is a measurement of force. Mary's weight is given in newtons, which is a unit of force. So the correct answer to the question 'What is Mary's weight?' is option b) 502 N.
Step-by-step explanation:
Calculating the Change in Potential Energy
To calculate the change in Mary's potential energy as she descends the stairs, we use the formula for gravitational potential energy, which is PE = mgh, where m is the mass, g is the acceleration due to gravity (approximately 9.81 m/s²), and h is the height.
Mary's weight in newtons is given as 502 N, so we can use this value to represent the force of gravity on her mass. Therefore, we don't need to calculate her mass separately because weight is the product of mass and gravity (W = mg). As a result, her mass would be W/g, where W is 502 N.
To find the change in potential energy:
- Determine her mass by dividing her weight by the acceleration due to gravity: Mass (m) = Weight (W) / g = 502 N / 9.81 m/s².
- Calculate the change in potential energy using the height (h) of 3.3 m: PE = mgh.
Substituting the values, we get:
PE = 502 N / 9.81 m/s² * 9.81 m/s² * 3.3 m.
The 9.81 m/s² cancels out, and we are left with:
PE = 502 N * 3.3 m = 1656.6 J.
Thus, the change in Mary's potential energy is 1656.6 joules.
What is Mary's weight?
Mary's weight is given in newtons, which is a unit of force. So the correct answer to the question 'What is Mary's weight?' is option b) 502 N.