# Math Help - Kinematic #1

1. ## Kinematic #1

Question: While chasing Mitch for destroying his bike, Skid does the following to his Pinto: He starts from rest and accelerates at 0.6 m/s^2 for 15 sec. Travels at a constant velocity for 2 mins. Slows to a stop with an acceleration of -.75 m/s^2. What is the total distance Skid travels?

What I did so far: v = v not + at
= 0 + (.6)(15)
= 9 m/s
x = x not + v not t + 1/2 at^2
= 9 (120s) = 1080 m
v = v not = at
-9 = -.75t
t = 12 sec
Then I plug 12 sec to the formula x = x not + v not t + 1/2 at^2 and got a weird number. I am really stuck. Thanks again for your help!

2. Originally Posted by jsu03

Question: While chasing Mitch for destroying his bike, Skid does the following to his Pinto: He starts from rest and accelerates at 0.6 m/s^2 for 15 sec. Travels at a constant velocity for 2 mins. Slows to a stop with an acceleration of -.75 m/s^2. What is the total distance Skid travels?
break it up into 3 parts ... find the displacement for each part.

$\Delta x_1 = v_0 t + \frac{1}{2}at^2$

$\Delta x_1 = 0 + \frac{1}{2}(0.6)(15^2)$

$\Delta x_2 = vt = (v_0 + at_1)t_2$

$\Delta x_2 = (0 + 0.6 \cdot 15)(120)$

$\Delta x_3 = \frac{v_f^2 - v_0^2}{2a}$

$\Delta x_3 = \frac{0 - 9^2}{2(-.75)}$

sum all three displacements.

btw ... this isn't calculus. you should post problems like this in the "other topics" forum.