Transcript acceleration - GEOCITIES.ws

ACCELERATION
Is this runner stable?
Why is he standing in such a strange position?!
In what direction is the athlete’s foot pushing?
But in what direction is the athlete going?
Which Law of Newton explains this?
Describe it.
If Newton came up with a 3rd Law of Motion we
must assume that there are 1st and 2nd Laws…
There are.
Newton’s 2nd Law of Motion is all about Acceleration.
So, what is ‘acceleration’?
A sprinter waits in the blocks, the
gun is about to go off, their speed
is …
a. 0 mps
b. 9 mps.
6 seconds into the race, and the
sprinter is now running at their
top speed of...
a. 0 mps
b. 9 mps.
The sprinter’s speed has…
a. stayed the same
b. changed
The sprinter’s speed has…
a. decreased
b. increased
So our sprinter has …. away from
the blocks.
a. velocitied
b. accelerated
The word to describe a steady
change of speed is…
a. acceleration
b. velocity
I hope you all answered
ACCELERATION
not VELOCITY!
So, the word to describe a steady
change of speed is…
a. acceleration !!!
not
b. velocity X
(ASIDE:
Q: What does ‘velocity’ mean
then?
A: You’ll find out in the next
slide-show… be patient!
END OF ASIDE)
Definition: Acceleration means a
change of…
a. underwear
b. speed
A runner with a high acceleration
will reach their top speed…
a. quickly
b. slowly
A runner with poor acceleration
will take a .... time to get up to
their top speed.
a. short
b. long
To accelerate an athlete must lean forward.
And the more they lean forward the more
they accelerate…
The less they lean forward the less they accelerate…
Until eventually their acceleration is…
Are these runners accelerating?
And if not then why not!!?
Isn’t it what they’re paid to do?!
Are these runners accelerating?
Why now?
When a runner leans forward there is extra force
(their weight) pulling them forward…
And it is Force that causes acceleration.
NEWTON'S 2nd LAW OF
MOTION
THE LAW OF
ACCELERATION
The larger the FORCE you use to
push something the more you can
change its speed
And…
If you use the same force on 2
different objects the lighter object
will have its speed changed more
Newton wrote this rule down as...
FORCE =MASS x ACCELERATION
...and the acceleration is in the
direction that the force is acting.
So when a sprinter starts he’s using all his force to
make himself accelerate as much as possible…
So where does all that force go?
Because runners gradually stop accelerating…
Surely these runners are trying as hard as when they
started the race?
With all this effort there must be Force being applied!
So if there is Force, why is there no acceleration?