Physics, Chemistry and Biology: Post your doubts here!

[Unknown202]

"A person uses a surfboard to ride every 30th wave crest towards the beach. The wave crest
travels at a speed of 1.6m/ s and the distance between each wave crest is 24m.
How many wave crests does the person surf in one hour?"plz i need a help in this question the final answer is 8 but idk the steps to get it plzzzzzzz help

 

[Ayesha Asif333]

"A person uses a surfboard to ride every 30th wave crest towards the beach. The wave crest
travels at a speed of 1.6m/ s and the distance between each wave crest is 24m.
How many wave crests does the person surf in one hour?"plz i need a help in this question the final answer is 8 but idk the steps to get it plzzzzzzz help

Is this an o level phy ques?

 

[Unknown202]

Is this an o level phy ques?

no igcse

 

[Unknown202]

Is this an o level phy ques?

can u help plz

 

[Ayesha Asif333]

no igcse

can u help plz

Sure, can u tell the year and ques no. PLZ

 

[Unknown202]

2017 feb march paper 22 q19

 

[Unknown202]

Sure, can u tell the year and ques no. PLZ

and can u tell me detailed steps

 

[Ayesha Asif333]

Hold on....

 

[Ayesha Asif333]

"A person uses a surfboard to ride every 30th wave crest towards the beach. The wave crest
travels at a speed of 1.6m/ s and the distance between each wave crest is 24m.
How many wave crests does the person surf in one hour?"plz i need a help in this question the final answer is 8 but idk the steps to get it plzzzzzzz help

Alright so we got the speed and the distance
Divide the two to get the time it takes for the wave crest to travel 24/ 1.6 =It takes 15s
Now in one hour the person can surf 3600/15= 240 wave crests
But in the beginning they said he only rides every 30th wave crest so divide 240 by 30 and u get ur final ans
Hope this is detailed enough

 

[Ayesha Asif333]

Good ques btw^^

 

[Unknown202]

Alright so we got the speed and the distance
Divide the two to get the time it takes for the wave crest to travel 24/ 1.6 =It takes 15s
Now in one hour the person can surf 3600/15= 240 wave crests
But in the beginning they said he only rides every 30th wave crest so divide 240 by 30 and u get ur final ans
Hope this is detailed enough

thx sooooooooooooooo much

 

[studyingrobot457]

Good ques btw^^

YOU STOLE MY CHANCe IN ANSWERING lol

 

[Ayesha Asif333]

YOU STOLE MY CHANCe IN ANSWERING lol

And robots only answer or act when they're asked to

 

[teachyourself]

read popular science books to learn stuff beyond your textbooks and enjoy science, science is about asking question not memorization
https://thepiratebay.org/search/michio kaku/0/99/0
https://thepiratebay.org/torrent/6818569/The_Stephen_Hawking_Ebook_Collection__(mobi)
https://thepiratebay.org/search/brian greene/0/99/0
https://thepiratebay.org/torrent/4788808/Matt_Ridley__Genome__The_Red_Queen_(E-books__PDF)
https://thepiratebay.org/torrent/13...Most_Astonishing_Scientific_Adventure_(gnv64)
https://thepiratebay.org/torrent/8521581/Genome__The_Autobiography_of_a_Species_in_23_Chapters_
https://thepiratebay.org/search/neil tyson/0/99/0
https://thepiratebay.org/search/sean carroll/0/99/0

 

[teachyourself]

And robots only answer or act when they're asked to

Google's Deep Mind Explained! - Self Learning A.I
https://www.youtube.com/watch?v=TnUYcTuZJpM

 

[studyingrobot457]

read popular science books to learn stuff beyond your textbooks and enjoy science, science is about asking question not memorization
https://thepiratebay.org/search/michio kaku/0/99/0
https://thepiratebay.org/torrent/6818569/The_Stephen_Hawking_Ebook_Collection__(mobi)
https://thepiratebay.org/search/brian greene/0/99/0
https://thepiratebay.org/torrent/4788808/Matt_Ridley__Genome__The_Red_Queen_(E-books__PDF)
https://thepiratebay.org/torrent/13...Most_Astonishing_Scientific_Adventure_(gnv64)
https://thepiratebay.org/torrent/8521581/Genome__The_Autobiography_of_a_Species_in_23_Chapters_
https://thepiratebay.org/search/neil tyson/0/99/0
https://thepiratebay.org/search/sean carroll/0/99/0

wow, first thing, you are using torrents, second thing you have mixed it up, this is a forum for a board exam, no one cares about this here, you would have posted in off topic, (I know what you are trying to do, you want to convince us about ath..)

 

[teachyourself]

wow, first thing, you are using torrents, second thing you have mixed it up, this is a forum for a board exam, no one cares about this here, you would have posted in off topic, (I know what you are trying to do, you want to convince us about ath..)

these books are about astrophysics/physics and genetics, could not find anything on chemistry yet, popular books in respective subjects are a good way to improve one's thinking approach for any subject, be it history, math, physics, psychology, etc

relying only on textbooks keeps the thinking limited and the grades low, check educational psychology and neurosciences research, at first sight these "popular science" or "popular history" etc books seem irrelevant but when you start reading them, the interest level increases and creativity develops in the background processes of the brain while awake (but when NOT studying the particular subject) and recall develops when sleeping (memory consolidation), also these popular science books give the brain the novelty aspect of learning, ultimately leading to a better understanding of a subject
https://www.sciencedaily.com/releases/2015/11/151119104105.htm (about creativity)
https://www.scientificamerican.com/article/your-best-creative-time-not-when-you-think/ (about creativity)

 

[Unknown202]

may june 2017 paper 21 question 29
A cylinder of conducting putty has length l, diameter d and resistance R. The putty is now
moulded into a cylinder of diameter 2d that has the same volume.

By which factor does the resistance of the putty cylinder decrease?

do anyone know how to solve it?

 

[studyingrobot457]

may june 2017 paper 21 question 29
A cylinder of conducting putty has length l, diameter d and resistance R. The putty is now
moulded into a cylinder of diameter 2d that has the same volume.

By which factor does the resistance of the putty cylinder decrease?

do anyone know how to solve it?

This is pretty basic stuff, we know that R is inversely proportional with cross section, so it must be inversely proportional to the square of the radius, I cannot explain it verbally, but just follow the steps

R↔1/A
so R↔1/r^2 (no pi here, because this is just proportionality)
so R↔1/(d/2)^2

now we can substitute any value, so we can see the proportionality
let d=1
so R = 1/0.25 = 4

now d is twice, so 2
R = 1/1 = 1

this means R was reduced by a factor of 4, so R/4

Ik this takes a lot to understand, but this is how I would think of honestly

Edit: or you could imagine that constant of proportionality should be one in which

R=1/(r)^2
R * (r)^2 = 1
(when d doubles r doubles too)
so R* 2r^2
R4r*2
we need to keep it to the same proportionality(cuz r^2 and R are always proportional) (=1)so R should be reduced by a factor of 4
R/4*4r^2=1
R*r^2=1 (back to proportionality, so it is reduced by factor of four)

hope the two explanation helps

 

[teachyourself]

This is pretty basic stuff, we know that R is inversely proportional with cross section, so it must be inversely proportional to the square of the radius, I cannot explain it verbally, but just follow the steps

R↔1/A
so R↔1/r^2 (no pi here, because this is just proportionality)
so R↔1/(d/2)^2

now we can substitute any value, so we can see the proportionality
let d=1
so R = 1/0.25 = 4

now d is twice, so 2
R = 1/1 = 1

this means R was reduced by a factor of 4, so R/4

Ik this takes a lot to understand, but this is how I would think of honestly

Edit: or you could imagine that constant of proportionality should be one in which

R=1/(r)^2
R * (r)^2 = 1
(when d doubles r doubles too)
so R* 2r^2
R4r*2
we need to keep it to the same proportionality(cuz r^2 and R are always proportional) (=1)so R should be reduced by a factor of 4
R/4*4r^2=1
R*r^2=1 (back to proportionality, so it is reduced by factor of four)

hope the two explanation helps

you should write a solution manual for all past papers of subjects you have done or are doing, the small reasoning tips for the answers have been done well, they could be a bit more detailed for students who are weak, a lot of students will benefit from your work if you decide to do it, one pastpaper per week or per 2weeks will let you complete sufficient number of pastpapers