Mary weighs 459 N and she walks down a
flight of stairs to a level 4.7 m below her
starting point.
What is the change in Mary’s potential energy?
To calculate the change in Mary's potential energy, we can use the formula:
Potential Energy = Mass x Gravitational Acceleration x Height
In this case, Mary's weight is equivalent to her mass multiplied by the gravitational acceleration. Assuming the standard acceleration due to gravity of 9.8 m/s², we can calculate her weight:
Weight = Mass x Gravitational Acceleration
459 N = Mass x 9.8 m/s²
Now, we need to find Mary's mass. We divide both sides of the equation by 9.8 m/s²:
459 N / 9.8 m/s² = Mass
Now, we can calculate the change in potential energy. Since Mary walks down a flight of stairs to a level 4.7 m below her starting point, the height is negative (-4.7 m) as it corresponds to a decrease in elevation:
Change in Potential Energy = Mass x Gravitational Acceleration x Change in Height
Change in Potential Energy = Mass x 9.8 m/s² x (-4.7 m)
Substituting the mass we found earlier:
Change in Potential Energy = (459 N / 9.8 m/s²) x 9.8 m/s² x (-4.7 m)
Now we can solve for the change in potential energy.