Calculating Time for Overtaking in a Race

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Homework Help Overview

The discussion revolves around a physics problem involving two race cars with different accelerations, starting times, and the goal of determining the time it takes for one car to overtake the other. The subject area is kinematics, specifically focusing on acceleration and motion equations.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss using the kinematic equation x = 1/2at² + Vi(t) to calculate the positions of both cars. There are attempts to apply this formula to find the time it takes for the sports car to overtake the stock car, but confusion arises regarding the correct application of time and the initial conditions.

Discussion Status

Several participants express uncertainty about their calculations and the application of the formula. There is a request for clarification on the values used in the calculations, particularly regarding the time variables for both cars. Some guidance is offered to revisit the setup and assumptions, but no consensus or resolution has been reached yet.

Contextual Notes

Participants are working under the constraints of the problem statement, including the initial conditions of both cars and the time delay for the stock car. There is an emphasis on understanding how to incorporate these factors into their calculations.

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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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