From your data what effect does changing the mass have on the period (for a
given value of the length L)?
Answers
direction of objects, and the distance between objects.
CONTEXT
This lesson helps students understand concepts related to how gravitational forces act on objects by exploring the motion of pendulums.
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MOTIVATION
Ask students the following questions in order to get a feel for their current knowledge and perceptions of pendulums. Answers to these questions are provided for you, but don't expect or lead students to these answers yet. At this point, simply gather and keep a good record of students' current ideas; students will have a chance to refine these after the website exploration that follows.
Questions to ask:
How would you define a pendulum?
(A pendulum is loosely defined as something hanging from a fixed point which, when pulled back and released, is free to swing down by gravity and then out and up because of its inertia, or tendency to stay in motion.)
How does a pendulum work? What are the parts of a pendulum?
(A simple pendulum consists of a mass (called the bob) attached to the end of a thin cord, which is attached to a fixed point. When the mass is drawn upwards and let go, the force of gravity accelerates it back to the original position. The momentum built up by the acceleration of gravity causes the mass to then swing in the opposite direction to a height equal to the original position. This force is known as inertia.)
What is the period of a pendulum?
(A period is one swing of the pendulum over and back.)
What is the frequency of a pendulum?
(The frequency is the number of back and forth swings in a certain length of time.)
What variables affect the rate of a pendulum's swing?
(Students may come up with a variety of answers, but the four that they will be testing in this lesson are:
Length of the pendulum-Changing the length of a pendulum while keeping other factors constant changes the length of the period of the pendulum. Longer pendulums swing with a lower frequency than shorter pendulums, and thus have a longer period.
Starting angle of the pendulum-Changing the starting angle of the pendulum (how far you pull it back to get it started) has only a very slight effect on the frequency.
Mass of the bob at the end of the pendulum-Changing the mass of the pendulum bob does not affect the frequency of the pendulum.
Force of gravity-This accelerates the pendulum down. The momentum built up by the acceleration of gravity causes the mass to swing in the opposite direction to a height equal to the original position.)