Distance Traveled By A CarKinematics Problemby haengbon Tags: acceleration, hard, kinematics, physics, velocity 

#1
Oct2909, 11:13 AM

P: 38

1. The problem statement, all variables and given/known data
a car traveling due east on a straight road and accelerates at a constant rate for 10(s) increasing its velocity from rest to 40 m/s. It then travels at a constant velocity for 5s and accelerates at a steady rate for the next 5s to a velocity of 20m/s. It travels at this velocity for 10s and then accelerates rapidly to a stop at a time of 2s. What is the total distance traveled by the car? All I know is, the answer NEEDS TO BE 770m. I'm trying to find the soltuion :( 2. Relevant equations none /:)? 3. The attempt at a solution I tried solving it first by drawing a diagram and then , paired up (40 m/s, 10s), (40m/s,5s) , (20m/s,5s), (20m/s,10s), (v=?,2s) then, I solved for the acceleration for each with V=Vo + at. after which, I solved for each of their distances with V(^2) = Vo(^2) + 2ad. for example, G: 40 m/s , 10s V = Vo+ at 40 = 0 + a(10) a = 4 m/s^2 V^2 = Vo2 + 2ad 1600 = 0 + 2(4)d d = 200 m I did the same thing with all the others and after reaching (20 m/s,10s), I got 900. I stopped there and didn't solve further cause I thought I wouldn't get the right answer anymore even if I did solve for (v=?,2s) . Can someone please guide me? :( I need to find out how to solve this because it would most likely be in the exam I need to pass just days away :( It looked simple at first but I'm going crazy solving it O.o 



#2
Oct2909, 11:26 AM

P: 122

Do you doublecheck your calculation? If yes but you still have wrong answer, please post your full solution.




#3
Oct2909, 11:27 AM

HW Helper
P: 4,442

Draw the timevelocity graph.
To find the total distance traveled by the car, find the area bounded by the graph with xaxis. It contains 2 triangles, two rectangles and one trapezium. 



#4
Oct2909, 09:33 PM

P: 38

Distance Traveled By A CarKinematics Problem
how do I draw a timevelocity graph :((? I'm sorry but I really don't know how to ___




#5
Oct2909, 09:33 PM

P: 38





#6
Oct2909, 09:56 PM

P: 17

Are 2 of your accelerations negative? If not, then I believe this is where you are making the mistake. For example, if you are going from 40 m/s to 20 m/s in 5s, this will have a negative acceleration since you are decreasing in velocity.




#7
Oct2909, 09:59 PM

HW Helper
P: 4,442

Take time on xaxis and velocity in yaxis.
Answer to the first part is correct. For second part, d2 = v*t. For third part vi = 40 m/s and vf = 20 m/s. Do the calculation as in the first part. repeat the same thing for reaming parts. 



#8
Oct3009, 03:48 AM

P: 38




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