#idk how to form the equation in order to solve for running speed

44 messages · Page 1 of 1 (latest)

south folio
slim sirenBOT
hollow axle
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hi

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do you have the answer

lime steeple
# south folio

You have to start by naming the variables, for example
c = cycling speed
r = running speed
t_c = time spent cycling
t_r = time spent running
d_c = distance traveled by cycling
d_r = distance traveled by running
Then you can start writing down equations between those variables

hollow axle
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@lime steeple

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idk if my way will work your probally right but

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if s= d/t the d = st

lime steeple
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yep

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Also, the exercise is giving you a relation between c and r

hollow axle
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therefore 60 = 48s + (s + 30) 16

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but i get a negtive number

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sorry i am jsut doing random questiosn for fun

hollow axle
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@lime steeple

lime steeple
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OK, I'm putting the answer in spoiler so that the OP can solve by themselves

hollow axle
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it would be cool if you tell me why my way never worked if you dont mind

lime steeple
# hollow axle therefore 60 = 48s + (s + 30) 16

||So you know that c=r+30 and that the total distance is 60 = d_c + d_r. But as you said distance is speed times duration so that d_c = c * t_c and d_r = r * t_r . You also know that t_r = 48/60 (all times should be in hours !) and t_c = 3*t_r. Now put everything together||

hollow axle
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oh got it thanks

lime steeple
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I'm guessing the reason you got a wrong answer is because you forgot to convert durations into hours

hollow axle
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ya i was using miniutes

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lol

lime steeple
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Yeah that's a common source of errors in physics problems ^^

south folio
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the answer is 15km/h according to my textbook

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did you guys get something else?

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I keep getting 48.75 kmph

lime steeple
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Did you convert minutes into hours in your computation ?

south folio
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to convert min to hour u just divide by 60 right?

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if it’s ok can u show me ur working out and I compare it to mine to see where I went wrong

lime steeple
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Maybe I made a mistake somewhere but I also got 48.75km/h

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Which would mean that she cycles at 78.75km/h

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That's not really human speeds but tbf to be able to cover 60 freaking kilometers in like an hour, you have to be super(wo)man

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That I just realized

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Actually I think there is something wrong in the exercise cause they say cycling takes up the most time, but they also say that the time she spent cycling is a third of the time spent running which is a contradiction

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Okay so I did a reverse computation assuming r=15km/h
I got that she spent a third time MORE cycling
So 48minutes times 4/3
Which makes sense

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There we go

south folio
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so by definition what the question meant by “she spent a third as much time again cycling” was that she cycled a third extra or the original time spent running+16 minutes?

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cool

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but I reckon the question kinda of badly written

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that was my bad I guess should’ve realised that earlier

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.solved