(solution) Student Exploration: Energy of a Pendulum Gizmos / Student Exploration: Energy of a Pendulum_answered 2021 100% COMPLETE SOLUTIONS DOWNLOAD TO SCORE OUTSTANDING GRADE A

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Student Exploration: Energy of a Pendulum

Vocabulary: conservation of energy, gravitational potential energy, kinetic energy, pendulum,

potential energy, velocity

Prior Knowledge Questions (Do these BEFORE using the Gizmo.)

1. A toy car is about to roll down a track, as

shown below. At what point do you think

the car will reach its greatest speed?

Mark this point on the image.

2. A pendulum consists of a weight that is

suspended from a pivot. At what point will

the pendulum below move fastest?

Mark this point on the image.

3. What do these two situations have in common?

Both the objects will reach their maximum speed at the lowest point.

Gizmo Warm-up

Objects have several types of energy. Potential energy depends on an object’s position or

shape. Kinetic energy is the energy of movement. The Energy of a Pendulum Gizmo™ allows

you to explore how the amounts of these types of energy change for a pendulum in motion.

1. On the DESCRIPTION pane, change the initial

angle (θ) to 40 degrees. Click Play ( ). How

does the velocity (speed and direction) of the

pendulum change as it swings from right to left?

The velocity increases as it comes down but slows down

when it reaches the side.

2. On the image at right, mark the point where the

pendulum swings fastest with an X. Then, circle the

two points where the velocity is zero.

Activity A:

Potential and

kinetic energy

Get the Gizmo ready:

• Click Reset ( ).

• Check that m is 0.5 kg, L is 2.0 m, g is 9.8 m/s2

,

and θ is 40 degrees.

Introduction: An object that is a certain height (h) above the ground has the potential to do

work, and therefore has potential energy. This type of potential energy is called gravitational

potential energy (GPE, or PE for short). The unit of energy is the joule (J).

Question: How are potential and kinetic energy related?

1. Observe: Select the BAR CHART tab. Click Play and observe. What do you notice about

the gravitational potential energy (PE), kinetic energy (KE), and total energy (TE)?

The PE is greatest when the ball is in a higher position and the KE is greatest when it's at the bottom of the swing

because that's when the velocity is greatest. The TE stays the same.

2. Measure: Click Reset. Turn on Show numerical values.

A. What is the gravitational potential energy? 2.3 J

B. What is the kinetic energy? 0 J

C. What is the total energy? 2.3 J

_

3. Measure: Click Play, and then try to click Pause ( ) when the pendulum is in the middle

of its swing. (This might require several tries.)

0 J

A. What is the gravitational potential energy now?

2.3 J

B. What is the kinetic energy now?

2.3 J

C. What is the total energy?

4. Analyze: At any given time, what can you say about the total energy of the pendulum?

The total energy of the pendulum is always 2.3 J

This illustrates the principle of conservation of energy. In a closed system, energy can be

converted from one form to another, but the total amount of energy remains the same.

(Activity A continued on next page)

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