Question

If you brake your car with constant acceleration and your initial speed was 12 m/s, what is your average speed during breaking?

Answer 1

So average speed is change in speed over change in time

Answer 2

um.....are you given anything else?

Answer 3

or are you supposed to make accerlation a variable?

Answer 4

Im not given anything else.

Answer 5

dangit, so that's a variable for time and acceleration then...

Answer 6

So Final speed = initial speed + accerlation*time

Answer 7

Final speed is 0.
0 = 12m/s + a*t

Answer 8

Change in speed is 12m/s

Answer 9

change in time is t

Answer 10

could we write it as (12/t)m/s

Answer 11

Yeah I guess?

Answer 12

Yeah, we'd have to subsitute a variable for time.

Answer 13

or -12

Answer 14

-12/a

Answer 15

yes.
so since theres no time given, I should just leave it like that I think?

Answer 16

Yeah. Maybe write t as (-12/a) seconds as well just to be safe.

Answer 17

wouldn't that be -1a m/s ? :o

Answer 18

uhh.
Sorry what? lol

Answer 19

So if change in velocity is 12m/s
And change in time is (-12/a) seconds

Answer 20

\[\frac{ 12m/s }{ (-12/a )s}\]

Answer 21

The a would go to the numerator, and it simplifies to -1

Answer 22

Thats true.

Answer 23

Would you say that the average speed is -a then?

Answer 24

yah

Answer 25

Alright, thank you :)