a runner starts from rest and speeds up with constant acceleration if she has gone a distance of 30 m at the point when she reaches a speed of 8 m/s, what is her acceleration

Answer 1

Givens:

v_i=0m/s

v_f=8m/s

d=30m

Formulas:

v_f²=v_i²+2ad

OR

d=1/2at²+v_it

v_f=v_i+at

Method 1

v_f²=v_i²+2ad

8²=0²+2a(30)

64/60m/s²=a=1.07m/s²

Method 2

d=1/2at²+v_it

30=1/2at^2+0t

30=1/2at^2

v_f=v_i+at

8=0+at

8/a=t

Plug into first equation

30=1/2a(8/a)²

60=64a/a²

60a=64

a=64/60m/s²=1.07m/s²