Assuming a typical efficiency for energy use by the body, how many slices of pizza must you eat to walk for 3.0 hr at a speed of 5.0 km/hr ? (Assume your mass is 68 kg).
To determine the number of slices of pizza you would need to eat in order to walk for 3.0 hours at a speed of 5.0 km/hr, we need to calculate the energy expenditure during walking and then divide it by the energy content of a slice of pizza.
Let's break down the steps to find the answer:
Step 1: Calculate the energy expenditure during walking
The energy expenditure, in kilojoules (kJ), can be determined using the formula:
Energy Expenditure = Power × Time
The power, in watts (W), is calculated using the formula:
Power = Force × Velocity
The force, in newtons (N), can be calculated using the formula:
Force = Mass × Acceleration
Acceleration is the rate at which the velocity changes over time, and since walking is a constant speed activity, the acceleration is zero.
Step 2: Convert energy expenditure to calories
To make the comparison with the energy content of the pizza slice easier, we'll convert the energy expenditure from kilojoules to calories. 1 kilocalorie (kcal) is equivalent to 4.184 kilojoules, so the conversion factor is:
1 kilojoule (kJ) = 0.239 kilocalories (kcal)
Step 3: Determine the energy content of a slice of pizza
The energy content of a slice of pizza can vary depending on the toppings and size, but on average, we can assume that one slice of pizza contains around 285 kilocalories or 1194 kilojoules.
Step 4: Calculate the number of slices of pizza needed
Divide the energy expenditure during walking (converted to kilocalories) by the energy content of a slice of pizza to find the number of slices needed.
Now, let's calculate the answer:
Step 1: Calculate the energy expenditure during walking:
The force is equal to the product of mass and acceleration, and since acceleration is zero, the force is zero.
Therefore, the power is also zero, and hence, the energy expenditure is zero.
Step 2: Convert energy expenditure to calories:
As calculated in Step 1, the energy expenditure is zero, so we don't need to convert anything.
Step 3: Determine the energy content of a slice of pizza:
Assuming one slice of pizza contains around 285 kilocalories or 1194 kilojoules.
Step 4: Calculate the number of slices of pizza needed:
Divide the energy expenditure during walking (which is zero) by the energy content of a slice of pizza.
Therefore, in this case, you do not need to eat any slices of pizza to walk for 3.0 hours at a speed of 5.0 km/hr.