Why Does a Pendulum Swing? | Sciencing
When the simple pendulum is set in motion, it moves back and forth periodically. The time it takes to make complete oscillation is called the frequency 'ƒ' of the. The back-and-forth motion of a swing is an example of a pendulum. The time it takes a pendulum to swing back to its original position is called A pendulum's period is related to its length, but the relationship is not linear. The pendulum swings back again, giving relief from the potential stress. then tend to swing back and forth, like a pendulum, between staying and leaving. the relationship and either attempts to make the relationship better.APPLICATION OF THE LAW OF CONSERVATION OF ENERGY TO A SIMPLE PENDULUM
The difficult notion is that an object in motion will continue to move unabated unless acted on by a force. To students, the things around them do appear to slow down of their own accord unless constantly pushed or pulled. The more experiences students can have in seeing the effect of reducing friction, the easier it may be to get them to imagine the friction-equals-zero case. Galileo Galilei was one scientist who studied gravitational forces.
In the late s, Galileo began to study the behavior of falling bodies, using pendulums extensively in his experiments to research the characteristics of motion. At the time, virtually all scholars still followed the belief of Aristotle that the rate of fall was proportional to the weight of the body. Galileo showed that this conclusion was erroneous based on the fact that air resistance slowed the fall of light objects.
Galileo was able to combine observation, experiment, and theory to prove his hypotheses. In easily verifiable experiments or demonstrations it can be shown that the period swing of a pendulum is independent of the pendulum's mass.
It depends instead on the length of the pendulum. This would suggest that objects fall at a rate independent of mass. The greater the amount of the unbalanced force, the more rapidly a given object's speed or direction of motion changes; the more massive an object is, the less rapidly its speed or direction changes in response to any given force.
In this lesson, students will explore websites with simulations of pendulums, where they'll be able to change the length and angle of the bob and observe its effects. They will then construct and test their own controlled-falling systems, or pendulums, to further observe and verify these theories. Read More 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. 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. Many students believe that changing any of the variables string length, mass, or where we release the pendulum will change the frequency of the pendulum. Give them a chance to debate and discuss their answers before continuing. Where do you see pendulums in everyday life?
How are they useful? Pendulums can be found in swing sets, grandfather clocks, swinging a baseball bat, and the circus trapeze. Pendulums are useful in timekeeping because varying the length of the pendulum can change the frequency. After your discussion, have students explore these websites: What is a Pendulum? After students have explored these sites, review with them their list of answers to the initial questions about pendulums, revising it with the current information based on the students' exploration of the websites.
As you review their answers to the question, "What variables affect the rate of a pendulum's swing? Read More Development Begin this part of the lesson by telling students that they will explore websites to learn more about how pendulums help us learn about gravitational forces. In the second part of the lesson, students will work in groups to construct their own pendulums and test what they have observed on the websites.
Have students run the demonstration called the Pendulum Lab. With this lab, students can play with one or two pendulums and discover how the period of a simple pendulum depends on the length of the string, the mass of the pendulum bob, and the amplitude of the swing. Make sure they understand how to run the experiment by telling them the following: With this demonstration, you can observe how one or two pendulums suspended on rigid strings behave.
You can click on the bob the object at the end of the string and drag the pendulum to its starting position.
Also, you can adjust the length and mass of the pendulum by adjusting the the controls in the green box on the right side of the page. The pendulum can be brought to its new starting position by clicking on the "Reset" button.
You also can measure the period by choosing the "photogate timer" option in the green box. Point out that the program measures the period, or one swing of the pendulum over and back.
Swinging with a Pendulum - Scientific American
How does changing the length of the bob affect the period? The shorter the length of the bob, the shorter the period will be. How does changing its starting point or angle affect the period? The smaller the angle, the shorter the period will be.
How can you get the shortest period? Decrease the length, and decrease the angle. How can you get the longest period? Increase the length, and increase the angle.
Explain why the pendulum continues to move without stopping or slowing down once it is set in motion. According to the law of inertia, a body in motion will continue in motion, unless acted upon by a force. Explain the features of this demonstration to your students: In this demonstration, you can vary the length of the pendulum and the acceleration of gravity by entering numerical values or by moving the slide bar.
Also, you can click on the bob and drag the pendulum to its starting position. This demonstration allows you to measure the period of oscillation of a pendulum. To participate in this demonstration, students should follow these steps: Press the "Start" button of the stopwatch just at the moment when the pendulum is going through its deepest point.
Count "one" when it goes again through its deepest point coming from the same side. Repeat counting until "ten. Dividing the time in the display by ten yields the period of oscillation. Students can also measure the frequency of a pendulum, or the number of back-and-forth swings it makes in a certain length of time.
By counting the number of back-and-forth swings that occur in 30 seconds, students can measure the frequency directly. What is meant by the period of oscillation? It is a way of measuring the back and forth swing of the pendulum. Inertia causes the pendulum to stay at rest unless a force causes it to move. When the wire and weight are moved in a straight motion, the weight and wire are acting under inertia.
This means that since the pendulum is now in motion, it keeps moving, unless there is a force that acts to make it stop. Gravity works on the pendulum while it is moving. The moving force becomes less as the force of gravity acts on the pendulum.
The pendulum slows and then returns to the starting point. This swinging-back-and-forth force continues until the force that started the movement is not stronger than gravity, and then the pendulum is at rest again.
The force of gravity is pulling the pendulum down toward the Earth.
Other forces act in opposition to the force of the moving pendulum. These forces are air resistance friction in the airatmospheric pressure an atmosphere at sea level, which lessens at higher altitudes and friction at the point where the top of the wire is connected. Its swing, called its period, could be measured.
However, later, as mechanical devices were developed, such as the pendulum clock, it was found that the length of the pendulum does change the period. Temperature changes result in a slight change in the length of the rod, with the result being a change in the period.