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How to do convert a negative velocity to speed? Alevel maths

hello,
This concept of mechanics does confuse me.
If I had a negative velocity of -24ms-1,
What would this be if I converted it to speed?

https://www.mathsgenie.co.uk/alevel/asmjune2019ans.pdf

For question 1c,
I did the whole method correctly, however I failed to identify that one of the speeds on the velocity time graph is 6ms-1

I wrote that speed as 24ms-1 as I did
Velocity = acceleration x time
Velocity = -12 x 2 = -24ms-1
And I just negated it to change it to speed
To 24 ms-1

Was I really just meant to subtract it and why?
Reply 1
Original post by harlz_chalamet
hello,
This concept of mechanics does confuse me.
If I had a negative velocity of -24ms-1,
What would this be if I converted it to speed?
https://www.mathsgenie.co.uk/alevel/asmjune2019ans.pdf
For question 1c,
I did the whole method correctly, however I failed to identify that one of the speeds on the velocity time graph is 6ms-1
I wrote that speed as 24ms-1 as I did
Velocity = acceleration x time
Velocity = -12 x 2 = -24ms-1
And I just negated it to change it to speed
To 24 ms-1
Was I really just meant to subtract it and why?

speed = |velocity|
as the negative sign for velocity just indicates a direction, the magnitude denotes speed (direction independent, so always positive). In gcse physics language, speed is a scalar, velocity is a vector.

If youre unsure, just work through the suvats with velocity, then take the absolute value to get speed. Though for this question, it should be fairly intuitive how speed would work. Choosing positive down (youre always falling towards the ground, then speed = velocity. When the parachute opens, you declerate so a=-2 between t = 3 and 5
(edited 2 months ago)

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