Need help ASAP - a level maths mechanics exam question

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TSRUser1231
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If anyone could help it would be greatly appreciated!

The height of a pole vaulter above the ground can be modelled using the equation h=1/60(125x - 12x^2) , where h metres is the vertical height of the pole vaulter and x metres is the horizontal distance travelled after his feet leave the ground.

a Find the horizontal distance travelled when the pole vaulter lands. (3 marks)
b Given that the pole vaulter is at his greatest height halfway between leaving the ground and landing, find the greatest height of the pole vaulter. (3 marks)
For a jump to be successful, the pole vaulter must clear a bar of height 4.9 m.
c Calculate the range of horizontal distances from the bar that the pole vaulter can leave the ground and have a successful jump. (7 marks)
d State the effect in this model of
i modelling the pole vaulter as a particle, (1 mark)
ii making air ressistance negligible. (1 mark)
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Pangol
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(Original post by TSRUser1231)
If anyone could help it would be greatly appreciated!
There are lots of parts to this, and you haven't said which pieces you are having problems with. On the basis that it may be all of it, let's start with (a). What is the value of h when the pole vaulter lands? How can this help you to find the horizontal distance travelled?
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TSRUser1231
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(Original post by Pangol)
There are lots of parts to this, and you haven't said which pieces you are having problems with. On the basis that it may be all of it, let's start with (a). What is the value of h when the pole vaulter lands? How can this help you to find the horizontal distance travelled?
for part a i got 25/12x -1/5x^2 = 0
25/12=1/5x
x=125/12
125/12 metres

but i need help with part b and part c
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Pangol
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(Original post by TSRUser1231)
but i need help with part b and part c
Part (b) - they make it very clear in the question that the maximum height occurs halfway between leaving the ground and landing. Using your answer to (a), what is the value of x at this point? How can that get you the maximum height?
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TSRUser1231
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(Original post by Pangol)
Part (b) - they make it very clear in the question that the maximum height occurs halfway between leaving the ground and landing. Using your answer to (a), what is the value of x at this point? How can that get you the maximum height?
for part b i got 125/12/2 = 125/24

1/60(125(125/24)-12(125/24)^2)

3125/576 is this correct?
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TSRUser1231
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for part c i got - h = 4.9
4.9=1/60(125x-125x^2)
294=-12x^2+125x
-12x^2+125x-294=0
a = -12 b=125 c=-294
use quadratic formula to get range 3.588m to 6.829m
do you think this is correct?
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TSRUser1231
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do you have any idea for part d? that would be very helpful
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Pangol
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(Original post by TSRUser1231)
for part c i got - h = 4.9
4.9=1/60(125x-125x^2)
294=-12x^2+125x
-12x^2+125x-294=0
a = -12 b=125 c=-294
use quadratic formula to get range 3.588m to 6.829m
do you think this is correct?
I think that everything you have done is correct, and that you would have the majority of the marks for it. I think there is one last thing you need to do to give an answer in context. What are they actually asking you for?
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TSRUser1231
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(Original post by Pangol)
I think that everything you have done is correct, and that you would have the majority of the marks for it. I think there is one last thing you need to do to give an answer in context. What are they actually asking you for?
range of horizontal distances?
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JoeC1999
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How did you get 3125/576?If you sub the numbers in the calculator that’s not what you get!
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JoeC1999
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(Original post by TSRUser1231)
for part a i got 25/12x -1/5x^2 = 0
25/12=1/5x
x=125/12
125/12 metres

but i need help with part b and part c
(Original post by TSRUser1231)
for part b i got 125/12/2 = 125/24

1/60(125(125/24)-12(125/24)^2)

3125/576 is this correct?
How did you get 3125/576 typing the numbers in calculator gives you a much difference answer
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Pangol
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(Original post by JoeC1999)
How did you get 3125/576?If you sub the numbers in the calculator that’s not what you get!
That's what I get when I put it into a calculator...

(Wow, nine month old thread!)
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lights123
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(Original post by Pangol)
That's what I get when I put it into a calculator...

(Wow, nine month old thread!)
Lolll i'm doing this question for tomorrow's HW right now
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mani89
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So what was the answer in c?
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mani89
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so what was the final answer for part c?I have a test tomorow help.
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