# F=maWatch

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#1
Can I calculate deceleration instead of acceleration using f=ma? Thank you
1
2 years ago
#2
(Original post by Eriikkaa)
Can I calculate deceleration instead of acceleration using f=ma? Thank you
Sure: deceleration is just negative acceleration!

If you want to find deceleration, you'll need work in the backwards direction, treating the force as positive. Keeping it negative would give you acceleration instead.
2
2 years ago
#3
(Original post by Eriikkaa)
Can I calculate deceleration instead of acceleration using f=ma? Thank you
deceleration is basically negative acceleration so yeah, if you find that "a" is a negative value, that will be deceleration.
2
#4
(Original post by Ed5)
Sure: deceleration is just negative acceleration!

If you want to find deceleration, you'll need work in the backwards direction, treating the force as positive. Keeping it negative would give you acceleration instead.
Thank you, this is really helpful
0
#5
(Original post by faiima)
deceleration is basically negative acceleration so yeah, if you find that "a" is a negative value, that will be deceleration.
Thanks!
1
2 years ago
#6
(Original post by faiima)
deceleration is basically negative acceleration so yeah, if you find that "a" is a negative value, that will be deceleration.
This isn't true in general. Deceleration in 1D problems occurs when the acceleration vector points in the opposite direction to the velocity vector of a body.

So for example, imagine a body of mass 5 kg moving at 10 m/s to the left. We would usually write that velocity as m/s i.e we would usually choose the +ve direction for vectors to be to the right.. If a constant force of 10 N acts on the body to the right, we would write N.

The resulting acceleration is then a=F/m = +2 m/s^2 which is +ve. However this force will decelerate the body since its velocity will change by +2 m/s every second. For example, at the end of the first second its velocity will be -8 m/s, which tells us that it is still moving to the left, but more slowly.
2
2 years ago
#7
(Original post by Eriikkaa)
Can I calc deceleration instead of acceleration with F = ma? Thanks
For slowing down, yes. Deceleration is the rate at which an object slows down (speed decreases), when net force opposes motion.

If motion's direction is +ve (common), a is -ve, so |a| is deceleration. If motion's direction is -ve, a is +ve, again deceleration |a|.

This treats deceleration as a scalar, typically so i.e) deceleration - 5 ms^-2 isn't sensible, acceleration is a vector so +/- 5 ms^-2 are equally valid.

(Original post by atsruser)
...
Agreed, strange replies here: https://www.thestudentroom.co.uk/sho....php?t=2190570

I fail to see how decelerating by - 5 ms^-2 makes sense or has merit. Deceleration as a vector strips out its utility or meaning i.e) rate of slowing down. In which case just use the acceleration vector.
2
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