Rocket Flying.
The two forces shown by the arrows are in opposite directions.
The upward force (called thrust) comes from the burning of fuel
at the bottom of the rocket (see also fireworks).
Hot
gases are forced downwards through the rocket's jets
which pushes the body of the rocket
upwards.
This is an example of Newton's Third Law.
The bigger the downward blast of gas,
the bigger the force (thrust)
pushing the rocket upwards
(a jet engine works in the same way to push an aircraft
forwards).
The downward force
(called "drag" or "air resistance")
is an example of friction.
It comes from the air pushing against the rocket as it moves.
The faster the rocket moves, the bigger the drag
because the air must be pushed out of the way at a faster rate.
There is also a contribution to the downward force
from the weight of the rocket (continued on the next page).
Note that the forces are usually
drawn by arrows
moving away from the
object as if they are pulling on it.
In reality, the thrust is pushing
upward on the bottom of the rocket
and the drag is pushing downwards on the top of the rocket.
It does not matter whether the
arrows are drawn pushing or pulling
as long as we know the size and
direction of the force.
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