PALS - Task with Student Directions

Pendulum

Task with Student Directions

6th Grade Performance Task
Contributed by: The RAND Institute (RAND)

Task:

A pendulum is a piece of wood, metal, wire, or other material that hangs from the top so it can move back and forth like a swing. Most pendulums have a weight at one end. Pendulums are often used to help large clocks keep time. Here is a picture of a pendulum.

Pendulums can swing at different speeds. Your job is to find out how the length and weight of a pendulum affect how fast it swings.

Materials:

Look at the placemat in front of you, and raise your hand if you are missing any of these items:

Platform and stick with hook at end
Long string
Short string
1 metal washer with hook
4 metal washers with hook
Ruler
Stop Watch
Pencil
Pendulum E on cardboard
Data Sheet (at the back of this booklet)

Directions:

Step 1: Practice using the stopwatch.

How to operate the stopwatch:

(a) Push the LAP RESET button. This will reset the stopwatch to 0 seconds.
(b) Push the START STOP button. The stopwatch will start, and will continue until you stop it.
(c) Push the START STOP button again. The watch will stop and will show the amount of time that has passed since it was started.

Step 2: Make Pendulum A (short string, 1 washer).

a. Attach the short string to the hook at the top of the stick.
b. Attach 1 washer to the bottom of the string.
c. Pendulum A should look like this:

Step 3: Practice timing the speed of the pendulum.

The time it takes to swing back and forth across the line 20 times is one way to measure the speed of the pendulum. Look at the picture and follow these instructions.

a. Reset the stopwatch to zero.
b. With one hand, pull the washer to the side so it just touches the stick.
c. With the other hand hold the stopwatch.
d. At the same time, start the watch and release the washer.
e. Count the number of times the washer crosses the line on the platform.
f. When the washer has crossed the line 20 times, stop the watch.
g. Read the time from the stopwatch.

Raise your hand if you have any questions.

Step 4: Measure the speed of Pendulum A.

Follow the directions in Step 3 to find the speed of Pendulum A.

How many seconds did it take the pendulum to swing across the center line 20 times?

Answer: _______ seconds

Step 5: Measure Pendulum A.

a. Use the ruler to measure the length of the string.

How many inches long is the string? Answer: ________ inches

b. Each washer weights the same amount. The greater the number of washers the heavier the pendulum.

How many washers were used? Answer: ________ washer(s)

Step 6: Write the results for Pendulum A on your Data Sheet (on the last page of this booklet).

a. Write the time it took Pendulum A to swing 20 times under the words "number of seconds needed for 20 swings."

b. Write how many inches long the string was under the word "length."

c. Write the number of washers under the heading "number of washers."

Step 7: Measuring the speed of Pendulums B, C, and D.

Here is a list of other pendulums you can make:

Pendulum B: short string with 4 washers
Pendulum C: long string with 1 washer
Pendulum D: long string with 4 washers

You need to make each pendulum and measure its speed. Repeat steps 4, 5, and 6 for pendulums B, C, and D. Record the time, the length of the string and the number of washers on your Data Sheet.

Step 8: Describe and explain your results.

1. Which two pendulums took the most time to swing 20 times?

2. Dale says the weight of the pendulum has the biggest effect on how fast it swings. Pat says the length of the string is more important. Who is right? ____________

Explain your answer.

3. Look at Pendulum E on the cardboard. How much time would it take Pendulum E to swing 20 times? (Circle one answer.)

a) More time than any of the other pendulums.

b) Less time than any of the other pendulums.

c) The same time as Pendulum A.

d) The same time as Pendulum B.

e) In between the times of Pendulum A and Pendulum D.

Explain your answer.

4. Do you think it was important to have the line drawn directly below the hook instead of closer to the base of the stick? (Check one answer.)

Yes ______

No ______

I'm not sure ______

Explain your answer.

Data Sheet

PENDULUM	NUMBER OF SECONDS NEEDED FOR 20 SWINGS	LENGTH (inches)	NUMBER OF WASHERS
A
B
C
D