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Forces and Motion

Falling Objects - A Cone Falling from a Cliff.

What are the Forces on a Falling Object?

The forces on a falling object are similar to the
flying rocket with the direction of the forces reversed.
In this example the falling object is a cone
but the same forces apply to any falling object.
Weight is the force pulling the cone downwards,
Air resistance (drag) is the force pushing the cone upwards.

When the cone first falls, there is a
downward force from the weight of the cone but very little drag
because the cone is moving slowly and air resistance is small.
The forces are unbalanced because there is a
large downward force but only a small upward force
and so the cone has a large acceleration
in the direction of the larger force (downwards)

Forces on a Falling Object

As the cone gets faster,
the drag increases and acceleration decreases
until the weight and drag are equal in size.
Now the forces are balanced and the cone will continue to
fall with a constant velocity called its terminal velocity.

What is Terminal Velocity?

The terminal velocity is the
fastest velocity that an object can have as it is falling.

The motion of the falling object
is shown on the velocity - time graph below.

Velocity - Time Graph for a Falling Object

The red curve shows the acceleration changing
from large to small.
The blue line shows the terminal velocity of the object.
The terminal velocity is always a constant velocity.

Calculations for falling objects are on the next page.

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