Phys Sci Lesson 12-6

Physical Sciences

Science

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Objective

Explain how air resistance affects moving objects.

air resistance- force that opposes the movement of an object in air

terminal velocity- speed at which air resistance and gravity acting on a
falling object are equal

vacuum- empty space

Key Terms

Falling Objects

Between an acorn from an oak tree and a leaf from the tree- which do you think will hit
the ground first? Why?

Poll

Between an acorn from an oak tree or a leaf, which one will land first?

• leaf

• acorn

• they land at the same time

Poll

If dropped from a height of 20 feet, which will land first, a small bouncy ball or a bowling ball?

• bouncy ball

• land at the same time

• bowling ball

Poll

On the moon, when dropped at the same time from the same height, which will land first, a feather or a hammer?

• feather

• land at the same time

• hammer

Falling Objects

●
another kind of force is air resistance- it opposes the downward
motion of objects through Earth’s atmosphere

●
the greater the surface area of an object, the greater the
resistance

●
The leaf has the greater surface area, so air pushes with more
force against it. The acorn hits the ground first.

Terminal Velocity

●
velocity- speed and direction

○
example: a car going 65 mph south on i680

○
(speed is only how fast something is going: rollercoaster moving 65
mph)

●
acceleration- rate of change in velocity

○
when a car changes speed or direction, it is accelerating

■
car speeds up= acceleration

■
car slows down= acceleration

■
a car goes around a corner= acceleration

●

Terminal Velocity continued

● gravity pulls an object toward Earth

● gravity causes the object to accelerate

● when the upward force of air resistance becomes equal to the

downward pull of gravity= object reaches terminal velocity

○ this means the object stops accelerating and velocity stays

the same

Open Ended

What happens to an object's velocity as it falls?

Free Fall

● vacuum= an empty space

● no air in a vacuum

● no air resistance in a vacuum

● there is no air on the moon

Free Fall continued

● Galileo Galilei

● NASA 1971- Astronaut David Scott

● IT’S ALL ABOUT AIR RESISTANCE!

Multiple Select

There is no ____________ in a vacuum.

• air

• matter

• velocity

• friction

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