Cycling: The energy behind it

I'm developing a school project (I'm studying software engineering) and it's about a sharing bicycles company. We need to calculate the total amount of necessary energy to travel from one point to another and the amount of k/calories burned by the user.

I need some help calculating the amount of kilocalories. I have these values as an example:

• User + bicycle = 85kg
• Distance: 1000m
• Inclination: 10%
• Duration: 180 seconds
• Speed: (around) 5.5 m/s
• Rolling resistance (coefficient): 0.004
• 1 kcal = 4186.8 J

My main problem is that the amount of kilocalories given by my calculations is around 334, which is huge.

• My main problem is that the amount of k/calories given by my calulations is around 334, which is huge. Please show us how you arrived at this?
– Gert
Dec 22 '18 at 18:26
• I assume that the answer is "yes", but is the bicyclist traveling uphill? Also, please be specific on what a 10% inclination means. Also note that 1 food calorie equals 1000 physics calories, so your answer may not be as far off as you think. Dec 23 '18 at 2:15
• My calculations were the following (considering no friction): totalEnergy = (0.5) * (75 kg + 10 kg ) * ( 5.5 m/s )^( 2 ) * 1000 m 1315635 J / 4186.8 J = 314 Sorry if this is really stupid but I didn't have physics so it's really hard for me to understand several topics. Dec 23 '18 at 22:37

You are leaving out a lot of variables, in particular air resistance (calculations here):

For example, in going from 7.5 mph to 20 mph:

1. mechanical resistance increases by 225%
2. rolling resistance by 363%
3. air resistance by 1800%.

and also how efficient the body is converting energy. According to another Physics.SE answer this is about 20% - see : How efficient is the human body?

Now ignoring all that and assuming air resistance is zero, the energy required to move the cyclist (and bike) is the same as the energy burned by the cyclist and nothing else (inertia for example) is involved then you should be looking at around 14 kcal.

There is a nice calculator here where you can check against your calculations.

• Thank you for your help. So if there isn't any friction at all, how should I calculate the amount of calories burned in my example? "Inclination: 10%" means "uphill slope", sorry for my bad grammar. Dec 23 '18 at 22:40