And today's question.

How do we describe and quantify movement?

What we already know

SPEED = DISTANCE/TIME 

 

 A normal journey.

From Sevilla to Huelva. 

Distance is 92.9 km

Google maps says it should take 1 hour (without traffic)

 

 

Calculate the speed...

SPEED = DISTANCE/TIME

92.9/1 

speed is 92.9 km per hour.

What information does this tell us?

  • Not very much really.

Text

Did the car stop for petrol? 

What was the fastest speed of the car?

What was the slowest speed of the car?

 

We know the car did not start at 92.9 km/h and then drive at a constant speed of 92.9 km/h until it reached Huelva then just stop.... but that seems to be what that information is telling us.

Or if the police stopped the car, and it was travelling at 130 km/h, can you defend yourself by saying "but my average speed was 92 km/h"

Car number 1

Car number 2

if the speed limit is the same for both, which can drive the fastest legally?

But which one gets faster, faster?

a =\frac{v - u}{t}
a=vut a =\frac{v - u}{t}

Acceleration is equal to the change in velocity divided by the time taken.

 

or

 

Acceleration = (final velocity - initial velocity)/time taken

a = \frac{v-u}{t}
a=vuta = \frac{v-u}{t}
at=v-u
at=vuat=v-u
v = u+at
v=u+atv = u+at

(ii)

v_{average}=\frac{v+u}{2}
vaverage=v+u2v_{average}=\frac{v+u}{2}
s=v_{average}. t
s=vaverage.ts=v_{average}. t
s=\frac{v+u}{2}.t
s=v+u2.ts=\frac{v+u}{2}.t
s=\frac{v+u}{2}.t
s=v+u2.ts=\frac{v+u}{2}.t
s=\frac{u+at+u}{2}.t
s=u+at+u2.ts=\frac{u+at+u}{2}.t
s=\frac{2u+at}{2}.t
s=2u+at2.ts=\frac{2u+at}{2}.t
s=ut +\frac{at^2}{2}
s=ut+at22s=ut +\frac{at^2}{2}

Your TWO equations to learn are then...

a = \frac{v-u}{t}
a=vuta = \frac{v-u}{t}
s = ut + \frac{1}{2}at^2
s=ut+12at2s = ut + \frac{1}{2}at^2

Where:

= initial velocity

 

=  final velocity

 

= displacement

 

= time

 

= acceleration

u
uu
v
vv
s
ss
t
tt
a
aa

Year 8 [week ending 18th March] Movement II

By Gavin King

Year 8 [week ending 18th March] Movement II

Movement, acceleration, equations of motion

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