**Answer:**

it would take approximately 232 to 258 D cell batteries to power a human for 1 day.

**Explanation:**

<em>Estimate the recommended daily food intake (in Food Calories).</em>

An average adult man requires between **2000 to 3000** calories per day.

<em>Estimate the daily energy (in joule) a human needs.</em>

As we know 1 food calorie is equal to 4.184 Joules of energy

2000*4.184 to 3000*4.184

**8368 to 12552 Joules**

But for engineering calculations 1 food calorie is equal to 1000 engineering calories, so

8368*1000 to 12552*1000

**8368000 to 12552000 Joules**

<em>Estimate the voltage (in volt) of one D cell battery</em>.

The voltage of a D cell battery is around **1.5 Volts**

<em>Estimate the charge (in amp-hours) of one D cell battery.</em>

The amp-hours of a D cell battery varies with the manufacturing company, the typical amp-hours are in the range of **6 to 10 amp-hours. **

<em>Estimate the energy of one D cell battery (in watt-hour).</em>

Energy in watt-hour is given by

voltage*amp-hour

1.5*6 to 1.5*10

**9 to 15 watt-hour**

<em>Estimate the number of D-cell batteries it takes to power a human for 1 day.</em>

First let us calculate the energy in a D cell battery,

1 watt-hour is equal to 3600 Joules

9*3600 to 15*3600

32400 to 54000 Joules

The number of D cell batteries required is found by dividing the energy need of a human by the energy stored in a D cell battery.

12552000/54000 to 8368000/32400

**232 to 258 batteries**

Therefore, it would take approximately 232 to 258 D cell batteries to power a human for 1 day.