Activity 3: Bullroarers
Lesson Objective:
Students will simulate the function a propeller by creating an ancient signaling device known as a bullroarer.
Set-Up:
Each student will need one craft stick, one index card, one rubber band and 2 paper clips. Groups of students can share measuring tape, string, markers and masking tape.
Demo and discussion:
Bullroarers have been used by many cultures, throughout many continents, for thousands of years. Anthropologists, scientists who study ancient cultures, have disputed whether or not bullroarers are musical instruments, signaling devices or both. Like many tools that human beings use, the bullroarer was probably used for multiple purposes. What is known is that a bullroarer’s unique sound can travel several miles in areas that are flat. Like many ancient …show more content…
Think of a propeller as a spinning wing. Like a wing, it produces lift, but in a forward direction—a force we refer to as thrust. Its rotary motion through the air creates a difference in air pressure between the front and back surfaces of its blades. In order for a propeller blade to spin, it usually needs the help of an engine. In cross section, a propeller is shaped like a wing to produce higher air pressure on one surface and lower air pressure on the other. Angle of attack is the angle a wing makes with the oncoming airflow. Pitch angle is the angle a propeller blade makes with its plane of rotation. A wing has nearly the same angle of attack across its entire length. But a propeller blade has a twist, so its pitch angle varies along its length. On a
Lesson Objective:
Students will simulate the function a propeller by creating an ancient signaling device known as a bullroarer.
Set-Up:
Each student will need one craft stick, one index card, one rubber band and 2 paper clips. Groups of students can share measuring tape, string, markers and masking tape.
Demo and discussion:
Bullroarers have been used by many cultures, throughout many continents, for thousands of years. Anthropologists, scientists who study ancient cultures, have disputed whether or not bullroarers are musical instruments, signaling devices or both. Like many tools that human beings use, the bullroarer was probably used for multiple purposes. What is known is that a bullroarer’s unique sound can travel several miles in areas that are flat. Like many ancient …show more content…
Think of a propeller as a spinning wing. Like a wing, it produces lift, but in a forward direction—a force we refer to as thrust. Its rotary motion through the air creates a difference in air pressure between the front and back surfaces of its blades. In order for a propeller blade to spin, it usually needs the help of an engine. In cross section, a propeller is shaped like a wing to produce higher air pressure on one surface and lower air pressure on the other. Angle of attack is the angle a wing makes with the oncoming airflow. Pitch angle is the angle a propeller blade makes with its plane of rotation. A wing has nearly the same angle of attack across its entire length. But a propeller blade has a twist, so its pitch angle varies along its length. On a