Question

At the end of a race, a runner decelerates from a velocity of 9.00 m/s at a rate of 2.00 m/s2 . (a) How far does she travel in the next 5.00 s? (b) What is her final velocity? (c) Evaluate the result. Does it make sense?

Answer 1

Answer: Distance travelled= 20m

Explanation:From given data,

u=9m/s  a= -2m/s^2(deccelertion)

(a) S= ut+1/2at^2  t=5s

S=9*5- 1/2*2*(5)^2= 45-25= 20m

(b) v=? v^2=u^+2aS

V^2=81-2*2*20=81-80=1

V=1m/s (if it asked for this time i.e., for 5 sec)

But her final velocity would be zero as it is deccelerating

if we doesn't consider time!!!