Calculating Time for Overtaking in a Race

[bigzee20]

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?

 

[tiny-tim]

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!

x= 1/2at² + Vi(t)

 

[bigzee20]

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??

 

[tiny-tim]

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.

 

[bigzee20]

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

 

[tiny-tim]

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?

 

[bigzee20]

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

 

[tiny-tim]

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

 

[bigzee20]

Iam confused man

 

[bigzee20]

can someone help me solve this?

 

[bigzee20]

Anybody?