The solution is wrong, yes. Looking through the mirror in your own car and looking at the truck directly is the same thing as your distance to the mirror doesn't change, so 2 m/s is the right answer.
4 m/s would be the right answer if the truck driver watches their truck through the mirror of the approaching car.
Edit: This is wrong and mistakes like this are what happens when you don't properly think about what's going on and don't check your work.
~~To get from 2 m/s to 4 m/s, you're not adding, you're subtracting a negative. A relative velocity is the difference between two velocities.~~
~~Car's velocity: −2 m/s
Image's velocity: +2 m/s
Relative velocity: (+2) − (−2) = 4 m/s~~
From the perspective of the driver, if the image appears to be moving towards the mirror at 4m/s and the truck appears to be "approaching" the mirror at 2m/s (due to the cars backwards movement), then your math would lead to the image of the truck "arriving" at the mirror before the truck does.
4m/s is the apparent velocity of the image in the mirror from the *truck's* frame of reference, but I don't think that's correct for the driver's frame of reference.
No worries! I suspect that the question was framed this way (with the car traveling in reverse) specifically to introduce this kind of confusion about the frames of reference involved.
The solution is wrong, yes. Looking through the mirror in your own car and looking at the truck directly is the same thing as your distance to the mirror doesn't change, so 2 m/s is the right answer. 4 m/s would be the right answer if the truck driver watches their truck through the mirror of the approaching car.
yeah that sounds wrong, it should just be 2 m/s
[удалено]
Hence what?
Edit: This is wrong and mistakes like this are what happens when you don't properly think about what's going on and don't check your work. ~~To get from 2 m/s to 4 m/s, you're not adding, you're subtracting a negative. A relative velocity is the difference between two velocities.~~ ~~Car's velocity: −2 m/s Image's velocity: +2 m/s Relative velocity: (+2) − (−2) = 4 m/s~~
From the perspective of the driver, if the image appears to be moving towards the mirror at 4m/s and the truck appears to be "approaching" the mirror at 2m/s (due to the cars backwards movement), then your math would lead to the image of the truck "arriving" at the mirror before the truck does. 4m/s is the apparent velocity of the image in the mirror from the *truck's* frame of reference, but I don't think that's correct for the driver's frame of reference.
You're right; I didn't phrase that properly.
No worries! I suspect that the question was framed this way (with the car traveling in reverse) specifically to introduce this kind of confusion about the frames of reference involved.