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# Where did i go wrong? Watch

1. https://3b0a7b1bc87f5381e60f8f717510...%20Edexcel.pdf

question 4

i got
s=2t-4.9t²-50
and
s=20-4.9t²

however when i equated them to find time i got a negative, if this was a real exam i'd obviously disregard the negative and just make the answer positive xD since it's time

18t=-50
2. (Original post by notnotbob)
https://3b0a7b1bc87f5381e60f8f717510...%20Edexcel.pdf

question 4

i got
s=2t-4.9t²-50
and
s=20-4.9t²

however when i equated them to find time i got a negative, if this was a real exam i'd obviously disregard the negative and just make the answer positive xD since it's time

18t=-50
I believe you went wrong in your first suvat, it should be as when t=0, the ball is 50m above the ground and not -50m
3. That gets the answer to be
4. (Original post by Cryptokyo)
I believe you went wrong in your first suvat, it should be as when t=0, the ball is 50m above the ground.
but i said s+50 not s-50

for the first particle it is 50 m above ground, thus taking ground height as S the first particle must have height s+50 not s-50 xD
5. The reason it that suvats lie to you. It is formally where is the initial displacement of the particle. In this case so it is

The problem your equation is that when ,

(Original post by notnotbob)
but i said s+50 not s-50

for the first particle it is 50 m above ground, thus taking ground height as S the first particle must have height s+50 not s-50 xD
6. (Original post by Cryptokyo)
The reason it that suvats lie to you. It is formally where is the initial displacement of the particle. In this case so it is

The problem your equation is that when ,
ah good point so the 50 should've gone on the other side anyway, thanks

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