Acar is moving southwest at a velocity of 10 meters per second. five seconds later, it's going 40 meters per second. what was the car's average acceleration during this time?

If "during this time" refers to the 5 second interval mentioned above, then the average acceleration is

Notice that we took the start time to be the start of the 5 second interval and set that to . The starting velocity is the velocity measured at the start of the interval, and is the velocity measured at its end.

So the average velocity over these 5 seconds is

when insulating materials rub against each other, they may become electrically charged . electrons , which are negatively charged, may be 'rubbed off' one material and on to the other. the material that gains electrons becomes negatively charged. the material that loses electrons is left with a positive charge.