How is Average Velocity Calculated in a Two-Part Journey?

[CrusaderX]

Hi guys, I just started taking physics 2 days ago at my school. One of our questions is:

"You drive a car 2.0 hours at 40km/h, then 2.0 hours at 60 km/h What is your average velocity?"

Ok, from what I understand, Average Velocity is:

delta v = delta distance / delta time

So, To find delta distance, I need to subtract 120 - 80 since 2 hours at 40 km/h is 80 and 2 hours at 60 km/h is 120.

And to get delta time, I'd have to subtract two from two... leaving zero. Well since you can't divide by zero, I'm stuck from here. I've looked at some sites online, but it's not helping me. Can someone help me out here? I'm guessing it's 50km/h from regular average, but I want to make sure.

Thanks in advance!

 

[civil_dude]

You need to think about this. I think you should do this in two parts.

Delta means final - initial, you are correct. But you can't do this all at once because it is NOT contiuous, i.e. the velocity jumps from one magnitude to the other.

So you have to find the initial distance and time, and add this to the next distance and time. I think you should take the total distance and divide it by the total time.