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When it comes to converting calories into joules, we rely on a fixed conversion factor. Food Calories, often listed simply as "Calories" with a capital 'C', are actually kilocalories in scientific terms.
1 Calorie is equivalent to 4184 joules. This means every calorie of energy consumed results in 4184 joules of energy. For example, if an exercise machine indicates that you've expended 2.5 Calories, you would multiply 2.5 by 4184 to convert, which gives you a total of 10460 joules.
This conversion is fundamental when calculating energy expenditure in scientific terms since joules are a standard unit used in physics.
Remember:

• 1 Calorie = 4184 joules
• For 2.5 Calories: Calculate 2.5 × 4184 = 10460 joules.

Understanding this relationship is crucial for tasks that link dietary energy with mechanical energy or power output.

Power, in a physical context, measures the rate at which energy is transferred or converted. It is calculated as the amount of energy used over a specific timeframe.
In this exercise, we have determined the energy expenditure to be 10460 joules. The time is 90 seconds, as 1.5 minutes is equivalent to 90 seconds.
To calculate power in watts, use the formula:

• Power (watts) = Energy (joules) / Time (seconds)

Substituting in our values, you calculate the power as \[\text{Power} = \frac{10460}{90} \approx 116.22 \text{ watts}.\]This tells you the average power output over the time interval of the exercise. Whether you're spinning on a stationary bike or lifting weights, understanding power output can help gauge the intensity of a workout.
Key points:

• Power is energy divided by time.
• For 10460 joules over 90 seconds, power is approximately 116.22 watts.

After calculating power in watts, it’s often useful to convert this figure into horsepower, especially when dealing with engines or motors where this unit is more commonly used.
1 horsepower is approximately equivalent to 746 watts. To convert watts to horsepower, divide the power in watts by 746. For instance, with a power output of 116.22 watts:

• Horsepower = Watts / 746

Divide 116.22 by 746 to get: \[\frac{116.22}{746} \approx 0.156 \text{ horsepower}.\] This means the exercise would be the equivalent of around 0.156 horsepower, showcasing the conversion of human power output to a more engine-friendly measurement. Remember:

• 1 horsepower = 746 watts
• With 116.22 watts, you get approximately 0.156 horsepower.

Understanding these conversions can make interpreting power outputs more intuitive across different systems and contexts.