Page 92 - Physics Form 5 KSSM_Neat

Effect of Lift Force on a Ping Pong Ball
Air
Lift force is produced from the difference Silicone tube
in pressure caused by the flow of air at
different velocities. Air flowing at a high
velocity above the ping pong ball as shown Filter funnel
KEMENTERIAN PENDIDIKAN MALAYSIA
in Figure 2.49 produces a region of low Region of high air
pressure. The difference between the speed and low
high pressure below the ball and the low pressure
pressure above the ball produces a resultant Ping pong ball
force upwards. This resultant force is the lift Region of
force that lifts up the ping pong ball. Lift force high pressure

Figure 2.49 Effect of lift force on the ping pong ball

Production of Lift Force by the Aerofoil

The aerofoil shape of the wing of an aeroplane causes air to flow at different speeds past the top
section and the bottom section. According to Bernoulli's principle, the higher air velocity at the
top section produces a region of low pressure while the lower air velocity at the bottom section
produces a region of high pressure. This difference in pressure produces a lift force acting upwards
on the aeroplane as shown in Figure 2.50.

Region of air flow at high velocity
creates region of low pressure

Lift force
Lift force

Aerofoil
Aerofoil
Air Drag
flow
Angle of attack

Chord line
Region of air flow at low velocity
creates region of high pressure
Figure 2.50 Production of lift force by the aerofoil Figure 2.51 Angle of attack on aerofoil

The total lift force acting on the aeroplane is also affected by the angle of attack as shown
in Figure 2.51. When the aerofoil is at a certain angle of attack, the aerofoil exerts a force on the
air flow. According to Newton's Third Law of Motion, a reaction force will act on the wing of the
aeroplane and contribute to the lift force that acts on the aeroplane.

82 LS 2.6.2