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Physics Form 4 Chapter 2 Force and Motion I

2.3 Free Fall Motion

Motion of object falling with and without air resistance

Valve
Rubber stopper
Air
Glass tube
Feather SPM Tips
To show the motion of free fall without vacuum, two objects
of the same size but different mass can be used. Chapter
Coin
Feather
Rubber Coin 2
stopper

Figure 2.37

1. At the beginning, the glass tube consists of air inside it. When the tube is inverted, the coin
reaches the base faster than the feather even though both started to fall at the same time.
2. Next, the tube is connected to a vacuum pump to draw
out the air from it. When all the air has been pumped
out, a vacuum is resulted in the tube.
3. When the tube is inverted, both the coin and the feather Connect to
vacuum pump
fall to the base at the same time.
• Discussion: In this case, both the objects fall without
air resistance. Coin
Feather
4. An object falling under the pull of the gravitational Air being sucked
force without any other forces acting on it is said to out of the tube
be undergoing free fall. Vacuum
5. An object undergoing free fall will accelerate. This
acceleration is known as gravitational acceleration.
The value of the gravitational acceleration does not
depend on the shape and mass of the object.

Figure 2.38

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