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# Which formulas would I use for these questions? watch

1. A sprinter accelerates from rest to a constant rate for the first 10 metres of the 100 metres. He takes 2.5 seconds to run the first 10 metres.

Find the acceleration of the sprinter during the first 2.5seconds of the race.

I thought it would be 10/2.5=4ms^-2 but the answer is actually 3.2ms^-2, please explain

Also--Show the speed of the sprinter at the end of the first 2.5 seconds of the race is 8ms^-1....please explain.

thank you
2. Have you learnt about the SUVAT equations?

You know that u = 0, s = 10 and t = 2.5. Can you find a?
3. (Original post by tommm)
Have you learnt about the SUVAT equations?

You know that u = 0, s = 10 and t = 2.5. Can you find a?
If I knew V i would do v^2-u^2/2as=a, but I don't so Im stuck
4. what other ones do you know of and can be used here?
5. (Original post by boromir9111)
what other ones do you know of and can be used here?
all the ones I know contain both V and A so I can't use them
6. You have s, u and t, and you need to find a. There is a formula for those variables

Spoiler:
Show
s= ut + 1/2at^2
7. (Original post by BuuTuu)
all the ones I know contain both V and A so I can't use them
above poster has answered it for you.
8. (Original post by Rubgish)
You have s, u and t, and you need to find a. There is a formula for those variables

Spoiler:
Show
s= ut + 1/2at^2
thank you, I get it now
9. As long as you know three of the variables, you can always find any of the other two .

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