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# Direct proportion question

1. A ball falls vertically after being dropped. The ball falls a distance, d metres, in a time of t seconds.
d is directly proportional to the square of t.

I worked out the first question which was the formula:

Another question was, calculate the time the ball takes to fall 605m

So i did

That was the final answer, however i was wondering, do i not divide by 5 to get t on its own?

If not for this one, do i ever? Or do you leave a number next to it always?

Thank you!
2. did you not divide by 5 to get from 605 to 121
3. (Original post by TenOfThem)
did you not divide by 5 to get from 605 to 121

Aaah right yeh! So it would just be

then Sqrt that? :O?
4. yup
5. (Original post by DeathByBSOD)
My Maths is kinda rusty, :s

so i think its:

Therefore,
~ 4.92s
This is incorrect ... the OP now has the correct answer
6. (Original post by DeathByBSOD)
My Maths is kinda rusty, :s but where did you get the 5 FROM?

so i think its:

Therefore,

the 5 is from the first part of the question, when 20 is directly proportion to 4k so k=5
7. (Original post by IgorYakov)
the 5 is from the first part of the question, when 20 is directly proportion to 4k so k=5

Ah Ok thanks.

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