Calculating Time for Overtaking in a Race

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The discussion centers on calculating the time it takes for a sports car, accelerating at 5.9 m/s², to overtake a stock car that accelerates at 4.1 m/s² and has a 1.4-second head start. The original poster attempted to use the formula x = 1/2at² + Vi(t) but arrived at an incorrect time of 4.68 seconds. Participants pointed out the need to correctly account for the time difference and the proper application of the formula for both cars. Clarifications were requested regarding the values used in calculations and the significance of the time variable in the equations. The conversation highlights the importance of accurately incorporating all variables in kinematic equations to solve the problem correctly.
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Homework Statement


A race car driver buys a car that can accelerate at 5.9m/s^2. The racer decides to race against another driver in a souped up stock car. Both start from rest, but the stock car driver leaves 1.4s before the driver of the sports car. The stock car moves with an acceleration of 4.1m/s^2. What is the time it takes the sports car driver to overtake the stock car driver.

i have tried solving it using the formula x= 1/2at+Vi(t) but i get 4.68s which is wrong what is it that iam not doing correctly?
 
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bigzee20 said:
i have tried solving it using the formula x= 1/2at+Vi(t) but i get 4.68s which is wrong what is it that iam not doing correctly?

Hi bigzee20! :smile:

x= 1/2at2 + Vi(t) :redface:
 
Hey tiny-tim thanks for the reply

I used that formula on both cars then i divided their positions and that's how i got 4.68sec which is wrong. I don't know what iam doing wrong??
 
bigzee20 said:
I used that formula on both cars then i divided their positions and that's how i got 4.68sec which is wrong. I don't know what iam doing wrong??

ok … show us what you did, and then we can see where the mistake is. :smile:
 
Car a 1/2(5.9)(2.015)+0(2.015)= 5.94425
Car b 1/2(4.1(0.615)+0(0.615)=1.26075

Then 5.94425/1.26075 = 4.71sec
 
bigzee20 said:
Car a 1/2(5.9)(2.015)+0(2.015)= 5.94425
Car b 1/2(4.1(0.615)+0(0.615)=1.26075

Where did 2.015 and 0.615 come from?

What happened to t2?

And what happened to 1.4s? :confused:
 
For Car a what do i put in as time? i know car b is 1.4s?

Car a = 1/2 (5.9)(?)^2+0(?)
Car b = 1/2(4.1)1.4^2+0(1.4) = 4.018
 
Last edited:
bigzee20 said:
For Car a what do i put in as time? i know car b is 1.4s?

You put t as time.

t, in the formula, is the unknown!

t0 for car b is 1.4s
 
Iam confused man :confused:
 
  • #10
can someone help me solve this?
 
  • #11
Anybody?
 
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