# I don't get SUVAT equations at all...

WatchPage 1 of 1

Go to first unread

Skip to page:

Basically we've been told to use one of those four equations.

To answer these questions:

To answer these questions:

- A car accelerates uniformly from rest and after 12 seconds has covered 40m. What are its acceleration and its final velocity?

S - 40m

U - 0 m/s

V - ?

A - ?

T - 12seconds

How can I work out the acceleration without the final velocity - V-U/T = or even the final velocity without the acceleration? :/

The fact that I have to use one of 4 possible equations frustrates me even more.

0

reply

Report

#2

(Original post by

...

**TerribleGrades**)...

0

reply

Report

#4

*edit* I'm an idiot

With SUVAT equations you only need 3 of 5 possible values to find ALL of the other values. If you are confused to what equations you need, you need not worry! As all you have to do is check what values you have and want to find that match up the with one of the equations.

Say for example, you have displacement, initial velocity and acceleration but want to find final velocity, you just use the equation with all four values, in this case you would have to use: v^2 = u^2 + 2as.

With SUVAT equations you only need 3 of 5 possible values to find ALL of the other values. If you are confused to what equations you need, you need not worry! As all you have to do is check what values you have and want to find that match up the with one of the equations.

Say for example, you have displacement, initial velocity and acceleration but want to find final velocity, you just use the equation with all four values, in this case you would have to use: v^2 = u^2 + 2as.

0

reply

Report

#5

(Original post by

I'll get you started,

Using your values:

S - displacement = 40

T - time - 12

Therefore we can deduce that the final velocity is: 40/12 = 3.33 m/s.

With SUVAT equations you only need 3 of 5 possible values to find ALL of the other values. If you are confused to what equations you need, you need not worry! As all you have to do is check what values you have and want to find that match up the with one of the equations.

Say for example, you have displacement, initial velocity and acceleration but want to find final velocity, you just use the equation with all four values, in this case you would have to use: v^2 = u^2 + 2as.

**Welshstig**)I'll get you started,

**final velocity is just simply: total displacement / total time**Using your values:

S - displacement = 40

T - time - 12

Therefore we can deduce that the final velocity is: 40/12 = 3.33 m/s.

With SUVAT equations you only need 3 of 5 possible values to find ALL of the other values. If you are confused to what equations you need, you need not worry! As all you have to do is check what values you have and want to find that match up the with one of the equations.

Say for example, you have displacement, initial velocity and acceleration but want to find final velocity, you just use the equation with all four values, in this case you would have to use: v^2 = u^2 + 2as.

2

reply

Report

#6

Well for the one you have stated, where you have S, U and T given, you can look at each of your suvat equations and deduce which one you can use to find one Unknown. The second equation, s = ut + 1/2at^2, when subbed with the information given leaves you with the unknown you're looking for, a.

E.g 40 = 0xt + 1/2a(12^2)

Rearrange for 80/144 = a

So essentially you have rearranged s = ut + 1/2at^2 to s/0.5t^2 = a

E.g 40 = 0xt + 1/2a(12^2)

Rearrange for 80/144 = a

So essentially you have rearranged s = ut + 1/2at^2 to s/0.5t^2 = a

0

reply

Report

#7

(Original post by

Incorrect that is the average velocity.

**Mistletoe**)Incorrect that is the average velocity.

0

reply

Report

#8

(Original post by

No that's nonsense I'm afraid.

**Mr M**)No that's nonsense I'm afraid.

1

reply

(Original post by

Well for the one you have stated, where you have S, U and T given, you can look at each of your suvat equations and deduce which one you can use to find one Unknown. The second equation, s = ut + 1/2at^2, when subbed with the information given leaves you with the unknown you're looking for, a.

E.g 40 = 0xt + 1/2a(12^2)

Rearrange for 80/144 = a

So essentially you have rearranged s = ut + 1/2at^2 to s/0.5t^2 = a

**Benb2000**)Well for the one you have stated, where you have S, U and T given, you can look at each of your suvat equations and deduce which one you can use to find one Unknown. The second equation, s = ut + 1/2at^2, when subbed with the information given leaves you with the unknown you're looking for, a.

E.g 40 = 0xt + 1/2a(12^2)

Rearrange for 80/144 = a

So essentially you have rearranged s = ut + 1/2at^2 to s/0.5t^2 = a

0

reply

Report

#10

(Original post by

Im sorry but where did you get 80/144 from?

**TerribleGrades**)Im sorry but where did you get 80/144 from?

40 / 1/2 = 80

Then, divide this by the t^2 (12^2) = 80/144

The 0 x t is equal to nothing, so it is just cancelled

0

reply

Report

#11

(Original post by

Im sorry but where did you get 80/144 from?

**TerribleGrades**)Im sorry but where did you get 80/144 from?

Plug in , and then see if you can work out from there.

0

reply

Report

#12

If you don't understand the concepts of SUVAT and why they work I'd suggest looking up how to actually derive them (without calculus to make it a bit easier) just to sort of "re-assure" yourself that they do actually work (and so you don't end up like me trying to break maths in some wonderfully whacky way).

0

reply

Report

#13

I would just choose 2 and 4 tbh.

You already got S, U and T so you just need to look at equations that don't have 2 unknowns ie. 1 and 3.

So you got 2 and 4 left.

Then, all you need to do is substitute the given info into the equations to get the answers.

Since this question is pretty simple and M1 (I assumed) is pretty much making things as simplified as they could so you don't need to fret too much (I think)

You already got S, U and T so you just need to look at equations that don't have 2 unknowns ie. 1 and 3.

So you got 2 and 4 left.

Then, all you need to do is substitute the given info into the equations to get the answers.

Since this question is pretty simple and M1 (I assumed) is pretty much making things as simplified as they could so you don't need to fret too much (I think)

0

reply

Thank you, guys! I think I'm getting the hang of it now.

- Initial velocity 5m/s, final velocity 36km/hr, acceleration 1.25m/s^2. Time and Displacement?

S = ?

U = 5

V = 36km/hr into m/s = 10

A = 1.25m/s^2

T = ?

So to work out the time, I figured equation 1 would be best as it only had one unknown:

v = u + a**t**

To get**time**on its own:

v-u / a

10-5 / 1.25 = 4s

To work out the displacement (s), I figured equation 2 or 4 would be best as they are displacement equations and I have no unknowns left anyway:

**Equation 4**: 0.5 x (u+v) x t

0.5 x (5+10=15) x 4 = 30

Therefore, displacement must be 30m.

0

reply

Report

#15

When I used SUVAT I wrote out each letter and put the corresponding values in with the one that the question asks you to find as ?, this helps you know which equation to use by looking at which one contains all those values.

1

reply

X

Page 1 of 1

Go to first unread

Skip to page:

### Quick Reply

Back

to top

to top