M.Johnson2111
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Hi,
Please can I have some help with part c of this question?

For part a I got, T = u/g

For part b I got, H = u^2/2g

So far I have found 3H = 3u^2/2g and using SUVAT

S = 3u^2/2g
U = u
V = ?
A = g
T = ? X - trying to solve

And then I was using my answer for part a , T and going to add this to the value of T when falling?

Any help please as cant get past this point yet?
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M.Johnson2111
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mqb2766
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(Original post by M.Johnson2111)
Hi,
Please can I have some help with part c of this question?

For part a I got, T = u/g

For part b I got, H = u^2/2g

So far I have found 3H = 3u^2/2g and using SUVAT

S = 3u^2/2g
U = u
V = ?
A = g
T = ? X - trying to solve

And then I was using my answer for part a , T and going to add this to the value of T when falling?

Any help please as cant get past this point yet?
You know s,a,u and want t. Which suvat is it?
Or think about the s-t relationship, how long does it take to fall double, quadruple the distance in terms of T? Why 3H, how far from the peak is that?
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M.Johnson2111
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Name:  CF25B2C8-C7CE-4825-87F9-88B0EAA9FB0F.jpeg
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Size:  147.2 KBI’ve got a quadratic as expected but there are two unknown values?
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mqb2766
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(Original post by M.Johnson2111)
Name:  CF25B2C8-C7CE-4825-87F9-88B0EAA9FB0F.jpeg
Views: 9
Size:  147.2 KBI’ve got a quadratic as expected but there are two unknown values?
Sure, I was expecting you to reject the suvat approach for this reason (messy to sort out). Sketch the quadratic (height) trajectory against time. What points can you mark on.
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M.Johnson2111
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How would I do this rejecting the SUVAT approach?

So to sketch this would I let ut = x or t = x? from my equation

If I let ut = x, there is a repeated root of x = 9.8
Would this be my final answer, t = 9.8? I dont quite understand how thatd make sense but by substitution I think mathematically accepted?
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mqb2766
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a) and b) strongly suggest splitting up the trajectory into time to peak, peak to floor. What are the displacements and times "travelled" during those times. Remember displacement is a quadratic function of time.
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M.Johnson2111
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Okay so a graph for time to peak and one for time to floor?
S when peaking is 885
Then S from peak to floor = -885?
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mqb2766
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(Original post by M.Johnson2111)
Okay so a graph for time to peak and one for time to floor?
S when peaking is 885
Then S from peak to floor = -885?
885? :banghead:
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M.Johnson2111
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Sorry Im looking at the wrong question

3u^2/2g? for displacement
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mqb2766
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(Original post by M.Johnson2111)
Sorry Im looking at the wrong question

3u^2/2g? for displacement
Have you sketched the quadratic displacement-time curve? If so, can you upload it.
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M.Johnson2111
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Is this for 3c?
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M.Johnson2111
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Right so on the y-axis, I have H which is the displacement and then time on the x-axis

Where does the quadratic, equation involving T come into this and do I use this?
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mqb2766
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(Original post by M.Johnson2111)
Is this for 3c?
That's the question Im answering.
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mqb2766
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(Original post by M.Johnson2111)
Right so on the y-axis, I have H which is the displacement and then time on the x-axis

Where does the quadratic, equation involving T come into this and do I use this?
Can you upload what you've sketched? Which suvat describes s-t relationship (not involving v)?
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M.Johnson2111
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Okay so from what I know T = u/g and H = u^2/2g
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M.Johnson2111
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S = ut + 1/2at^2
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Ive literally just got my axis labelled, trying to find the H and T values to be able to sketch
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mqb2766
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(Original post by M.Johnson2111)
S = ut + 1/2at^2
So s-t is a quadratic curve with a max at the point in a) b)
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mqb2766
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(Original post by M.Johnson2111)
Ive literally just got my axis labelled, trying to find the H and T values to be able to sketch
A sketch doesn't have to be exact. You know the relative heights and times, that's all that's needed.
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