Calories generated in brakes of a machine

In summary: No, 1 kcal seems reasonable to me. 3m/s is not very fast. I would not expect the generated heat to be enough to boil off a litre of water!
  • #1
Karol
1,380
22

Homework Statement


A 1000 kg mass car is driving at 3 [m/sec], how many kcal develop in the brakes till full stop

Homework Equations


Kinetic energy: [itex]E=\frac{1}{2}mv^2[/itex]
Energetic equivalent of a kcal: 4186 [joule]

The Attempt at a Solution


##E=\frac{1}{2}1000\cdot 9=4500[joule]##
##\frac{4500}{4186}=1.07[kcal]##
It should be 1000 times bigger, 1,075[kcal]
 
Physics news on Phys.org
  • #2
Karol said:

Homework Statement


A 1000 kg mass car is driving at 3 [m/sec], how many kcal develop in the brakes till full stop

Homework Equations


Kinetic energy: [itex]E=\frac{1}{2}mv^2[/itex]
Energetic equivalent of a kcal: 4186 [joule]

The Attempt at a Solution


##E=\frac{1}{2}1000\cdot 9=4500[joule]##
##\frac{4500}{4186}=1.07[kcal]##
It should be 1000 times bigger, 1,075[kcal]
I get your answer. Is there perhaps a confusion between decimal comma and decimal point?
 
  • #3
by you get my answer you mean you also get the same result? i don't know if there's a confusion between a comma and a decimal point, but please tell me if the result of 1 kcal is reasonable? it isn't, right? so my answer isn't correct
 
  • #4
Karol said:
by you get my answer you mean you also get the same result? i don't know if there's a confusion between a comma and a decimal point, but please tell me if the result of 1 kcal is reasonable? it isn't, right? so my answer isn't correct
I mean I agree with your answer, a bit over one kcal. But in continental Europe, that could be written 1,075, no?
 
  • #5
I don't know about europe, I'm interested in my result. 1.07 kcal seems to me too low for that mass and speed, isn't it? and 1075 cal are gram calories, the heat needed to raise the temperature of one gram of water. my result is indeed 1075 gram calories, but i ask about kg calories, kcal. i think the answer must be 1075 kcal, it seems more reasonable
 
  • #6
Karol said:
I don't know about europe, I'm interested in my result.
Bear in mind that I do not know where you are or where your textbooks come from. Many on these forums are in continental Europe. I'm trying to understand why you are told the right answer is "1,075 kcal", when you and I both calculate it as just over 1 kcal.
1.07 kcal seems to me too low for that mass and speed, isn't it? and 1075 cal are gram calories, the heat needed to raise the temperature of one gram of water. my result is indeed 1075 gram calories, but i ask about kg calories, kcal. i think the answer must be 1075 kcal, it seems more reasonable
No, 1 kcal seems reasonable to me. 3m/s is not very fast. I would not expect the generated heat to be enough to boil off a litre of water![/QUOTE]
 
  • #7
You are probably right. but to boil 1 liter, from 00 to 1000 we need only 100 kcal, so 1075 is much more than to boil 1 liter of water, no?
 

What are "Calories generated in brakes of a machine"?

"Calories generated in brakes of a machine" refers to the amount of heat energy produced and released during the braking process of a machine.

How are "Calories generated in brakes of a machine" measured?

"Calories generated in brakes of a machine" are typically measured using a calorimeter, which is a device that measures the heat energy released during a chemical or physical process.

Why is it important to understand "Calories generated in brakes of a machine"?

Understanding the amount of "Calories generated in brakes of a machine" is important for determining the efficiency of the braking system and ensuring that the machine is not overheating or wasting energy.

What factors affect the amount of "Calories generated in brakes of a machine"?

The amount of "Calories generated in brakes of a machine" can be affected by factors such as the speed and weight of the machine, the type and condition of the brakes, and the duration of the braking process.

How can the amount of "Calories generated in brakes of a machine" be reduced?

The amount of "Calories generated in brakes of a machine" can be reduced by using more efficient brakes, reducing the speed and weight of the machine, and implementing strategies such as regenerative braking to capture and reuse some of the energy generated during braking.

Similar threads

  • Introductory Physics Homework Help
Replies
11
Views
2K
  • Introductory Physics Homework Help
Replies
7
Views
790
  • Introductory Physics Homework Help
Replies
3
Views
1K
  • Introductory Physics Homework Help
Replies
5
Views
1K
  • Introductory Physics Homework Help
Replies
4
Views
1K
  • Introductory Physics Homework Help
Replies
12
Views
2K
  • Introductory Physics Homework Help
Replies
3
Views
6K
  • Introductory Physics Homework Help
Replies
2
Views
2K
  • Introductory Physics Homework Help
Replies
5
Views
1K
Replies
9
Views
1K
Back
Top