Transcript Alchemy

Newton’s Third Law
Imagine a rocket is being launched from
the earth.
Hot gases are pushed out from the
bottom of the rocket as the rocket is
thrust upward.
The force of the gases pushing against
the surface of the earth is equal and
opposite to the force with which the
rocket moves upward.
The motion of the rocket can be
explained by Newton's third law, for
every action there is an equal and
opposite reaction.
The earth and the moon are
like two rocks in space. Why
does the moon orbit the
earth orbit the moon?
The force on each body is the same
– but in opposite directions
(Newton’s 3rd Law).
The moon is accelerated much more
than the earth, because it has so
much less mass than the earth
(Newton’s 2nd Law).
Your empty hand is not hurt because
there is little mass, therefore there is
little inertia (little resistance to a change
in motion).
Carrying a heavy load causes pain
because there is significant mass and
inertia, therefore your hand is tougher
to stop and continues to move.
As a result, your hand gets squashed
a bit and it hurts.
There is no net force on the horizontal
direction of the parcel being dropped from
the plane or the ball being dropped from
the mast.
As a result, it will continue to move at the
same speed of the plane or ship.
The parcel or ball will move the same
amount as the plane or ship.
http://www.bigs.de/en/shop/anim/flug01.swf
Bob’s weight is applying 500N on his
bosun. The rope used can hold 300N,
however Bob is using two ropes. As a
result, the bosun can support up to 600N.
When Bob reties the bosun, he ties one
end to the flag pole and it breaks.
This occurs because the force Bob’s
weight applies on the rope is 500N,
greater than the amount that a single
rope can support (300N).
We know if an object is not moving or
moving at constant speed in a straight
line there are still forces acting upon it.
Because there is no change in motion,
we can assume that there is NO net
force acting on the object.
Thus, the forces acting upon the
object counteract each other.
If the car is traveling at a constant speed,
there is NO net force acting on it.
We still need to step on the gas to
maintain the constant speed. This is
required to counteract the forces of
friction (ground and air).
These forces are in opposite directions
so that the net force is zero.
If you push with a force of 200N to slide a
box across the floor at a constant speed
in a straight line, how much friction is
exerted by the floor on the box?
200N in the opposite direction, there must
be zero net force in order that the box in a
straight line at a constant speed.
If Mark starts pulling on the rope, they
both move towards each other.
Mark’s pull on the rope is transmitted to
Sua causing her to accelerate towards
Mark.
By Newton’s 3rd Law, the rope pulls
back on Mark with equal force causing
him to accelerate towards Sua.
Each page is like a different body, so
when the nail is hit, there is a chain of
collisions taking place on the pages all
the way down to her head.
As a result, there is little change in
motion of the last page on top of her
head, so it doesn’t hurt.
The stack of books consists of many pages
that are at rest. They all have inertia
(because they all have mass) so they
resist accelerating (they resist a change to
their rest).