Calculating Car Collision Distance: A Kinematic Approach

[canucklekid]

A car starts at rest and accelerates to 7.5 m/s/s towards a 18 wheeler truck headed towards the car at a constant speed of 130 km/h. if they are 500m apart how far from the cars starting position will they collide


im really just having problems solving this i always seem to screw it up i finished all other questions with ease just not this one i feel i am probably making a stupid mistake somewhere in my calculations

btw if there has been a thread similar to this one could you please post a link i did a brief search but didnt come up with anything similar

 

[Feldoh]

What have you tried so far?

 

[Anden]

Hmm, is there no value for the acceleration of the car? Or is the car traveling at 7,5 m/s at the starting point?

 

[Mark44]

Hmm, is there no value for the acceleration of the car? Or is the car traveling at 7,5 m/s at the starting point?

The car's acceleration is given (somewhat unclearly) as 7.5 m/sec².

A car starts at rest and accelerates to 7.5 m/s/s

 

[canucklekid]

btw my buddy (older friend in university engineering) says the answer is 220m

 

[canucklekid]

the way the question is written to me it sounds like its stopped and instantly is magically able to accelerate to 7.5m/s/s

 

[Anden]

The car's acceleration is given (somewhat unclearly) as 7.5 m/sec².

You're right, missed that. :)

What you have to do is try to express the distance traveled by the two vehicles.

 

[Anden]

btw my buddy (older friend in university engineering) says the answer is 220m

Your buddy is right, but how do you get there?

 

[canucklekid]

i don't know how he solved it but i want to know if anyone knows please speak up I am trying to find out but he's out right now will let you know if i find out but let's try to solve it in the mean time

 

[kuruman]

It would really help you and us if you followed the template for homework help. What are the relevant equations? Hint: There are four and they are collectively called the kinematic equations. Which of these equations is the most likely candidate to help you set up the problem?

 

[Anden]

Ok, set the distance traveled by the car to d1 and distance traveled by the truck to d2.
d1 + d2 = 500, the time traveled by both vehicles is the same. So if you can express the distance traveled with respect to time for both vehicles and then put those two equations together and solve for time, you get the answer.

 

[canucklekid]

yes sorry i thought it was relitivley obvious that the kinematic equations would be used in this thanks for all the help guys