### Equations of Motion - Higher

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• #### Message 1.

Posted by BitesizePhysicsTeacher (U15165682) on Tuesday, 4th December 2012

We use most of the same symbols in Higher Physics for moving objects, though there are different symbols for distance, d, (a scalar) and displacement, s, (a vector).

Most of the time the directions of displacements, velocities and accelerations are important in Higher Physics, so we'll stick with the vectors ofr these equations of motion.

As before -

(1) s = v t
[constant velocity]

(2) s = ½ (u + v) t
[uniform acceleration]

(3) a = (v - u) / t

These can be combined to give two other equations -

(4) s = u t + ½ a t²

and

(5) s = (v² - u²) / 2 a
[this one is especially useful as it doesn't involve time, t]

As for all problems, by identifying the information in the question, and more importantly the information that is *not* in the question, we can choose the correct equation to start.

Examples -

A) a car accelerates from rest to 12 m/s in 8 seconds. How far does it travel?
[we have u, v and t, but not a, so we use equation (2) above]

s = ½ (u + v) t = ½ x (0 + 12) x 8 = 48 m

B) the same car brakes, accelerating from 12 m/s at - 4 m/s² for 2 seconds. How far does it travel?
[we have u, a and t, but not v, so we use equation (4) above]

s = u t + ½ a t² = 12 x 2 + ½ x (-4) x 2² = 16 m

C) A racing car accelerates at 8 m/s² from 5 m/s to 25 m/s. How far does it travel?
[we have u, v, and a, but not t, so we use equation (5) above]

s = (v² - u²) / 2 a = (25² - 5²) / (2 x 8) = 37.5 m

• #### Message 2

, in reply to message 1.

Posted by Hiza (U14875141) on Tuesday, 8th January 2013

really useful, thank you, im studying mechanics in physics, i need to get top notch at these suvat equations, the exam boards love em!

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