land speed record of 13.9 for birds is held by emuu. an emu starts with this speed running south straigh?

Question

slows down to 11 in 3 secs what is bird's velocity after an additional 4s has lapsed

Answer 1

What I understand from the problem, is that we need to find the desacceleration caused by the emu.

So, let's take initial velocity of the bird as : 13.9

and final velocity : 11

time = 3 s

using : Vf = Vo - at ; Vf = final speed ; Vo = initial speed.

11 = 13.9 - 3a

3a = 2.9

a = 0.95 m/s^2 >>>> desacceleration

Taking now, 11 m/s as initial velocity

let's find the final velocity after 4 s

Vf = 11 - 0.95*4

Vf = 7.2 m/s

Hope that helped