Question

A steam engine has an efficiency of 20%.It is given an energy of 1000 cal.per minute.What is the actual work done by it in joule and in calories?

a) 100 cal,800 J

b) 200 cal,873 J

c)10 cal,80 J

d)100 cal,100 J

Answer 1

@amistre64 @ParthKohli @hartnn @Callsito @Zarkon @Hero @.Sam. @estudier @ganeshie8 @ajprincess @Algebraic!

Answer 2

@Callisto

Answer 3

im not sure since we havent gone over this in my physics class yet, but i would say that 20% efficiency means that 20% of the 1000 cals are used; giving us 200 cals in the answer at least

Answer 4

May I help?

Answer 5

please do :)

Answer 6

ofcourse @SheldonEinstein

Answer 7

;) OK so first of all what @amistre64 discussed in his previous comment is very imp. to do this quest., so @mayankdevnani do you know what does efficiency mean?

Answer 8

ok @amistre64 then

Answer 9

yaa

Answer 10

efficiency=winout/winin*100

Answer 11

right @SheldonEinstein

Answer 12

Yeah or in simpler words it is : \(\large{\frac{\textbf{Output}}{\textbf{Input}}\times 100}\) it is 100%...

Answer 13

yaa

Answer 14

So, what we have is output/input * 100% = 20% , correct?

Answer 15

correct

Answer 16

Ok so now, let me understand the second line of the quest. , is the output = 1000 calorie ?

Answer 17

yaa

Answer 18

then

Answer 19

@SheldonEinstein then

Answer 20

Oh sorry wait!

Answer 21

yaa

Answer 22

I am getting diff. answer so I am checking it, sorry , it will require some patience.

Answer 23

ok

Answer 24

Quest. is wrong

Answer 25

why?? no it is right

Answer 26

Time is not given.. though if you take 1 minute it is 200 cal.

Answer 27

yaa

Answer 28

See , Power = 1000 cal/minute (given)

Answer 29

use this and you will get 200 cal. as answer.

Answer 30

so what's the work done?

Answer 31

W = P * time
if T = 1 second , W = P ...
that's it , find P(output) .. (using efficiency = Ouput/Input *100%) in Cal. per minute , that will be your answer

Answer 32

200 cal.... = WORK DONE

Answer 33

no

Answer 34

but the work done is in joule

Answer 35

@ParthKohli @Preetha

Answer 36

@SheldonEinstein

Answer 37

@myininaya

Answer 38

Is my answer correct, i.e. 200 cal, 873 J ?

Answer 39

yaa

Answer 40

So where is the problem? ?? ? ?

Answer 41

873 J how??

Answer 42

@amriju

Answer 43

@SheldonEinstein how you got it 873J

Answer 44

I got 200 Cal, and it is in options, soo....

Answer 45

but it's wrong

Answer 46

i need solution

Answer 47

can you help me @amriju

Answer 48

200 cal * 4.184 = 836 J (approx. ) not equal to 873 Joule , hence I think the options are wrong..

Answer 49

no it was not wrong

Answer 50

work done is 20 percnt of the energy given...thats efficiency....so per minute is 20percnt of 1000 cal...thats 200 cal...convert to joules

Answer 51

so 1cal.=? j @amriju

Answer 52

4.2...approx..the correct is 4.187...

Answer 53

is it 4.37

Answer 54

nope

Answer 55

why??

Answer 56

thats how it is defined...both are units...and 1 cal is defined as 4.187 joules...

Answer 57

That is what I was saying @amriju

Answer 58

in my solution book...the answer is as follows-

\[\frac{20}{100}=\frac{W}{1000}=200 calorie\]
OR
\[200\times4.37=873J\]

Answer 59

is that right?? @amriju and @SheldonEinstein

Answer 60

That is wrong, 1 Cal. = 4.187 Joule NOT 4.37 joule...

Answer 61

ok... thnx... @SheldonEinstein and @amriju

Answer 62

u may jst check on wikipedia...and its seems that none of the options are correct...the closest being 200, 837

Answer 63

just for reference

http://www.wolframalpha.com/input/?i=200+calorie+to+joule

Answer 64

if your options are truely: 200,873

then its most likely a typo and prolly meant to be read as 200,837