Question

I need help
h t t p : / / w w w .j i s k h a . c o m/ d i s p l a y . c g i ? i d = 1 2 5 0 8 1 6 5 0 6
Don't know how to do that one

or this one
h t t p : / / w w w . j i s k h a . c o m / d i s p l a y . c g i ? i d =1 2 5 0 8 1 5 4 2 0

Thanks!!!

Answer 1

The 100 m dash can be run by the best sprinters in 10.0 s. A 62 kg sprinter accelerates uniformly for the frist 45 m to reach top speed, which he maintains for the remainding 55 m.

(a) What is the average horizontal component of force exerted on his feet by the ground during acceleration?

(b) What is the speed of the sprinter over the last 55 m of the race (i.e., his top speed)?

ok I know how to do (b) once I know how to do (a)

it's just that (a) makes no sense because in order to find the force you need to find the acceleration for the first part of the race...

for the first part of the race we know the displacement is 45 but we need to know the acceleration which I don't know how to find

V = Vo + at

dosen't work

X = Xo + Vot + 2^-1 a t^2

also dosen't work because need to know t for first part of race

V^2 = Vo^2 + 2a(X - Xo)

dosen't work don't know V after first part of race

average V = 2^-1 (V + Vo)

dosen't work no a variable

so I'm out of equations... =[

Answer 2

try an equation with mass considering they tell you he weighs 62kg

Answer 3

shutup.

Answer 4

A = Vf - Vi
-------
Tf - Ti