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What is the Motion
of a
Flying Rocket?
Continued from the previous page.
When the rocket takes off, there is a large
thrust
from the engine but very
little drag because the
rocket is moving slowly and air
resistance is small.
The forces are unbalanced
because there is a
large upward
force but only a small downward force
and so the rocket has a large acceleration
in the direction of the
larger force
(upwards).
As the rocket gets faster,
the drag increases and acceleration decreases
until the thrust and drag are equal in
size.
Now the forces are balanced
and the rocket will continue with a constant
velocity.
The motion of the rocket
is shown on the velocity -
time graph below.
The red
curve shows acceleration changing from large to small.
The blue line shows constant
velocity.
This is the same shape
of velocity - time
graph
as a falling object
reaching its terminal velocity.
The next page shows how to calculate forces and acceleration.
Links
Forces and Motion
Force
Revision Questions
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