SCIENCE CONCEPT:
- Lift is an aerodynamic force which affects the flight
of a golf ball. Given the proper spin a golf ball can produce lift. A
ball driven with a spin about a horizontal axis with the top of the ball
coming toward the golfer produces a lifting force.
STUDENT OBJECTIVE:
- The student will graph the 'flight' of a golf ball
from ground level to its height of flight and then back down to the
ground.
OVERVIEW:
- The student will throw the golf ball from point A to point B
observing the 'flight' of the ball. The student will then graph his/her
findings about the 'flight' of the ball and give an explanation of why
the golf ball can gain lift describing Bernoulli's Principle.
TEACHER TEXT:
- Given the proper spin a golf ball can produce lift.
Originally, golfers thought that all spin was detrimental. However, in
1877, British scientist P.G. Tait learned that a ball, driven with a spin
about a horizontal axis with the top of the ball coming toward the golfer
produces a lifting force. This type of spin is known as a backspin. The
backspin increases the speed on the upper surface of the ball while
decreasing the speed on the lower surface.
The dimples also help in the generation of lift. By
keeping the flow attached, the dimples help promote an asymmetry of the
flow in the wake.
If the golf ball is given a spin about its vertical axis,
the ball will be deflected to the right for a clockwise rotation and to
the left for a counter-clockwise rotation. The generation of an
aerodynamic force by a spin about the axis perpendicular to the flight
path is known as the Magnus effect. The Magnus effect is important in
most ball games.
During the last part of a golf ball's flight, the
gravitational forces become dominant. As the balls velocity decreases
due to the drag imposed upon it, the lift decreases. At some point, the
lift will no longer be greater than the weight and the ball will begin
falling to the ground.
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PREPARATION TIME:
- 10 minutes.
LESSON TIME:
- 30 minutes.
TEACHER PREP:
- Gather materials
WORDS TO KNOW:
- aerodynamic force
- lift
- backspin
- Bernoulli principle
- pressure differential
- velocity
- finite lift
- gravitational forces
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