Year 10 Term 2 - Activity

Ticker Timer Activity [print-friendly version]

Aim:

- To investigate the effect of different types of motion on the spread of dots on the tape.

- To calculate the acceleration of a falling mass.

Materials:

Ticker timer Power pack connecting leads

timer tape 100 g mass carbon paper disc

metre ruler masking tape scissors

Procedure:

1. Connect the ticker timer to the A.C. terminals of the power pack (50 Hz) as directed by your teacher. Thread the ticker tape through the slots and under the carbon paper disc. Check that the ticker timer is working and that clear dots are being marked on the paper.

2. Pull a short piece of tape through at constant speed. Cut out a section that provides an adequate trace. Mark your initials on the back. (You will need this for your report). Repeat for each member of the group. Turn off the timer when not in use.

3. Attach a piece of tape, about 1 m, (long enough to reach the floor from the bench top), to a 100 g mass using a piece of masking tape. Thread the end of the tape through the ticker timer. Turn on the ticker timer. Let the mass fall to the floor. Detach the tape and repeat for each member of the group. Mark your initials on the back. (You will also need this for your report).

Results:

• Paste in the constant velocity trace, (or a small section of it), and label ‘Constant Velocity Trace’.

• Mark a starting position on the second tape. (This may not be the first dot but rather the first of the dots that can be counted. Draw a straight line across your tape through this dot and continue to draw a straight line across your tape at each successive 5th dot. (N.B. there should be 5 spaces between dots in each segment). See below.

• Cut your tape into sections along your drawn lines. (Mark each one on the back according to its order e.g. 1st section, 2nd section, etc.) Paste sections side-by-side into your report to make a bar graph. See below. This graph is a displacement time graph.

Time (tocks = 0.1seconds)

• Copy the table below into your report and complete for the first four or five sections. (Note: The ticker timer operates at mains frequency (50 Hz). Therefore there are 50 dots per second. Each 5-dot interval corresponds to 0.1 seconds (1 tock). The length of each interval corresponds to the distance travelled in 0.1 s.)

• Calculate the acceleration of the falling mass.

a = (v 2 - v 1)/t

Note: If 5 sections are used the time interval between the 1st and 5th section is 4 x 0.1 = 0.4s.

If 4 sections are used the time between the 1st and 4th section is 3 x 0.1 = 0.3s.

1. Use your data to draw a velocity time graph.

Questions:

• (a) Comment on the spread of dots on your trace with the constant velocity.

(b) Calculate this velocity.

(c) How would this trace change if the velocity were (i) higher? (ii) lower?

• (a) How do you know from your second tape that the object was accelerating?

(b) How does the shape of your displacement-time graph illustrate this?

• Explain why the velocity calculated for each section in your table was an average velocity.
• What was the calculated acceleration of your falling mass?
• What was the total length of your tape? This is the displacement of your falling mass.
• Refer to your velocity-time graph for the following questions.
• What is the shape of this graph? What does this tell you about the change in velocity?
• Calculate the slope of your graph – (rise over run).
• What doe this slope equal?
• Calculate the area under your velocity-time graph.
• Compare your calculated value of acceleration of your falling mass to the actual value of acceleration due to gravity (g) of 9.8 m/s 2. What factors have contributed this variation?
• Can you suggest any improvements to this activity?