00:01
A motorist on a road trip drives at different speeds, constant speeds, for these different legs of the trip.
00:10
So, maybe let's write these out a little bit, so do a little timeline here.
00:18
So first he drives for 50 minutes, and then for 6 minutes, and then for 55 minutes, and then he has a 30 -minute lunch somewhere in there.
00:33
I can erase this then.
00:38
So somewhere in there is a 30 minute lunch that doesn't matter a ton where that happens.
00:45
So 50 minutes, 6 minutes, 55 minutes, and 30 minutes.
01:01
And his speeds during this, he's going at 65 kilometers per hour, and then 75 kilometers per hour.
01:15
And then 50 kilometers per hour.
01:24
And then obviously when he's at the rest stop or whatever at the gas station, zero kilometers per hour.
01:31
So what is average speed? so average speed, which is not a vector, is the distance traveled over the total time, right? okay, so how far did he go? well let's actually name these uh...
01:58
We'll call this v1 v2 v3 and v4 i'll call the times correspondingly v1 v2 v3 and v and by v i mean t i'm going to try t is not vs okay t1 t2 t3 t4 okay so remember kinematics, distance equals velocity times time.
02:34
So what distance did he travel? v1, t1, plus v2, t2, plus v3, t3, plus v4, which is zero, times t4...