# When do you use SUVAT and when do you use the simple speed=distance/time?Watch

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#1
Hi,
This may seem a bit simple but is there a rule?
Also is there any equations that apply to specific examples? Eg: for free fall, i tend to find that i use s= ut + 1/2at^2
0
4 years ago
#2
(Original post by huwgerard1)
Hi,
This may seem a bit simple but is there a rule?
Also is there any equations that apply to specific examples? Eg: for free fall, i tend to find that i use s= ut + 1/2at^2
hello and welcome to TSR physics.

No rules other than choosing the form which suits the variables of the question you are answering. No more and no less.

The unknown variable must also be included in the equation. You may well have to manipulate the equation to make the unknown variable the subject though.

It's a case of deciding which SUVAT most efficiently meets the needs given the known and unknown variables.

For instance if you are given u, s and t and asked to find the final velocity, you don't need an acceleration term to answer so you would pick

and rearrange to make v the subject.

Similarly, if you are given v, u and s but no t, then asked to find acceleration, use

and rearrange to make a the subject.

Sometimes the SUVAT can be used in it's original form if the variables allow:

i.e. if you are given u, a and t and asked to find s, use

As I said, look at the known and unknown variables and choose the one that matches accordingly.
1
#3
(Original post by uberteknik)
hello and welcome to TSR physics.

No rules other than choosing the form which suits the variables of the question you are answering. No more and no less.

The unknown variable must also be included in the equation. You may well have to manipulate the equation to make the unknown variable the subject though.

It's a case of deciding which SUVAT most efficiently meets the needs given the known and unknown variables.

For instance if you are given u, s and t and asked to find the final velocity, you don't need an acceleration term to answer so you would pick

and rearrange to make v the subject.

Similarly, if you are given v, u and s but no t, then asked to find acceleration, use

and rearrange to make a the subject.

Sometimes the SUVAT can be used in it's original form if the variables allow:

i.e. if you are given u, a and t and asked to find s, use

As I said, look at the known and unknown variables and choose the one that matches accordingly.
Hi!! Thank you for your welcome and thanks for the help
0
4 years ago
#4
(Original post by huwgerard1)
Hi,
This may seem a bit simple but is there a rule?
Also is there any equations that apply to specific examples? Eg: for free fall, i tend to find that i use s= ut + 1/2at^2
Use s = vt for constant velocity. Use SUVATs for constant acceleration. Use calculus for variable acceleration.
1
4 years ago
#5
The SUVAT equations only apply in situations where you have a body moving in a straight line with uniform acceleration or deceleration. To find the correct equation to use in a given situation, write out s = ?, u = ?, v = ?, a = ?, t = ?, replacing ? with the given values. Assuming that you know the SUVAT equations, then choose the appropriate equation in order to find the missing quantity.
0
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