Kinematic Equations Used to Find A.) Average Speed & B.)Acceleration

[lethalfresa]

Homework Statement

A truck covers 40.0m in 7.15 s while uniformly slowing down to a final velocity of 3.50 m/s. a.) Find the truck's original speed b.) Find it's acceleration

Homework Equations

Δx = Vav(Δt) = (V+Vo/2)Δt

a=(V-Vo)/(Δt)

The Attempt at a Solution

Part A.)


1.) I used the formula Δx = Vav(Δt) = (V+Vo/2)Δt

2.) Plugged in what is given & solved for Vo

40.0m=((3.50m/s=Vo)/(2))(7.15s)

Vo=12.5 m/s

Part B.)

1.) I used the formula a=(V-Vo)/(Δt)

2.)Plugged in what I have

(3.50 m/s-12.5 m/s)/(7.15s) = -1.26 m/s2

Apparently both my answers are wrong and I am not sure what I am doing wrong. I tried this multiple times, as well as other different versions of this problem which I get correctly.

Your input would be appreciated. Thanks :)

 

[olivermsun]

40.0m=((3.50m/s+Vo)/(2))(7.15s)

Vo=12.5 m/s

Check your algebra here.

Part B.)

1.) I used the formula a=(V-Vo)/(Δt)

2.)Plugged in what I have

(3.50 m/s-12.5 m/s)/(7.15s) = -1.26 m/s2

It will be correct when you fix your V_o.