OCR M1 Urgent Help Needed Please Guys !!! Watch

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rayman198
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HEY GUYS I GOT A LITTLE PROBLEM HERE , THIS QUESTION IS FROM JUNE 04 MECHANICS 1 (ocr)

6)
A PARTICLE STARTS FROM REST AT O AND TRAVELS IN A STRAIGHT LINE TO A. THE TIME TAKEN FOR THE JOURNEY FROM O TO A IS 25s, AND THE PARTICLE REACHES A WITH A SPEED OF 15ms-1. THE VELOCITY OF THE PARTICLE t SECONDS after it leaves O is v ms-1, were v=kt^2, where k is a constant

i) Show that k = 3/125 (already done this one)
ii) Find the distance OA (tried this but aint 2 sure of my answer, please help)
iii) Find the distance of the particle from O when its acceleration is 0.725 ms-2

Thanks in advance guys !!
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yusufu
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(Original post by rayman198)
HEY GUYS I GOT A LITTLE PROBLEM HERE , THIS QUESTION IS FROM JUNE 04 MECHANICS 1 (ocr)

6)
A PARTICLE STARTS FROM REST AT O AND TRAVELS IN A STRAIGHT LINE TO A. THE TIME TAKEN FOR THE JOURNEY FROM O TO A IS 25s, AND THE PARTICLE REACHES A WITH A SPEE OF 15ms-1. THE VELOCITY OF THE PARTICLE t SECONDS after it leaves O is v ms-1, were v=kt^2, where k is a constant

i) Show that k = 3/125 (already done this one)
ii) Find the distance OA (tried this but aint 2 sure of my answer, please help)
iii) Find the distance of the particle from O when its acceleration is 0.725 ms-2

Thanks in advance guys !!
ii) integrate the speed equation:
s = 1/125 t³ + C ( when t = 0, s=0 so C=0)
s= 1/125 t³
s = 1/125 (25)³ = 125m

iii) differentiate the speed equation:
a = 6/125 t
0.725 = 6/125 t
t = 0.725*125/6 = 15.1s

put this into the distance equation:
s= 1/125 t³
s= 1/125 15.1³ = 27.6m
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