NAME: ……………………………………….. CLASS: …… DATE: ………………………..

PRACTICAL NO.: …….

Using a ticker timer to measure the acceleration of a falling mass.

This is a group experiment with two to four learners in a group (depending on the numbers in the class). The experiment could also be done as a demonstration by your teacher.

AIMS:

1. To interpret the dots on a ticker tape to identify uniform acceleration.2. To use the dots produced on the tape to determine the acceleration of the mass.3. To use the velocity values calculated from the tape to draw a velocity vs. time graph for the

mass.

INSTRUCTIONS:

1. Pay careful attention during the pre-prac talk and take notes so that you are sure what you have to do when you carry out the investigation.

1. Decide on and write up an action plan to measure the acceleration of a falling mass, using a ticker timer. You must provide a suitable mass yourself.

2. Carry out the measurement, taking due care regarding the voltage requirement of the timer.3. Analyse the tape and present the results in a tabular form.4. Determine the acceleration of the mass and compare this with the accepted value for the

acceleration due to gravity.

PROCEDURE:

1. Describe your action plan, including a statement of the problem, the apparatus that you will use and the method that you will follow.

2. Carry out your investigation taking the necessary readings and measurements.3. Record your results in a suitable table, showing the displacement of the mass in each

successive chosen time interval.4. Explain from these displacements whether or not the mass appears to be falling with

constant acceleration.5. Calculate the average velocity for each successive time interval.6. Draw a velocity vs time graph for the mass and comment on its shape.7. Calculate the acceleration of the falling mass. Comment on its agreement with that of the

acceleration due to gravity.8. Discuss the factors that could have caused any apparent errors or deviation.

ASSESSMENT:

Consult the rubrics on the next page that will be used to assess your work. Ensure that you have attempted to carry out all the requirements. The total number of marks allocated to the practical is given on the rubric sheet.

NAME: ……………………………….……………. CLASS: ………………. DATE: ……………………..

Assessment of measurement of acceleration of a falling mass

Assessment of group work skill

CRITERIA Competency level

Not Achieved1

Partially achieved2

Achieved3

Works co-operatively with others, each having a part to play

1 2 3

Performs prac without needing instruction. Knows what to do and is well prepared

1 2 3

(6)Assessment of analytical skills

CRITERIA Competency level

Not Achieved1

Partially achieved2

Achieved3

Learner ignores first few indistinguishable dots which are 1 2 3Learner divides tape up into suitable “time units”

1 2 3 (6)

Assessment of recording skills Description of competency level Competency level

All readings are correctly recorded in a clear, logical manner, demonstrating an understanding of the process required for the correct analysis of the tape

4

Readings are correctly recorded, but in a haphazard manner without a logical structure 3

Readings are recorded, but there are errors in the recording that will influence the outcome of the investigation negatively

2

Some readings are recorded, but there is clearly no understanding of the procedure that is being followed to achieve a successful outcome.

1

(4)Assessment of interpretation of data

CRITERIACALCULATION Competency level

Learner carries out calculation correctly with correct use of the period of the timer, the “time unit” being used, calculation of average velocities in each time unit and the identification of the points on the tape where the average velocity equals the instantaneous velocity. Correct calculation of the acceleration.

4

One error made in the above 3More than one error made in the above 2

Attempt to carry out the calculation demonstrates no understanding 1

(4)CRITERIA

GRAPH Competency levelGraph drawn correctly, with heading, axes labelled correctly (with units), points plotted correctly, identification that graph is to be straight (within limits of experimental error), graph drawn as best straight line through the points. 4One error made in the above. 3More than one error made in the above. 2

Attempt to draw graph demonstrates no real understanding of how a graph is to be drawn. 1

(4)Maximum marks: 24 Mark achieved: ………….

Sample results from this experiment:

Ticker tape: This diagram is not to scale.

Direction of tape:

The frequency of the ticker timer was 50 Hz.

Symbols Distance in mmA - B 9 mmB - C 12.6 mmC - D 16.2 mmD - E 19.8 mmE - F 23.4 mmF - G 27 mm

H - I 30.6 mmI - J 34.2 mmJ - K 37.8 mmK - L 41.4 mm

Hints:1. Determine the period of the timer: T = 1/f2. Determine the ave. velocity A – C3. Determine other ave. velocities – say C – E, and/or G – I, and/or J – L etc.4. Find the ave. acceleration for the tape.5. Compare this value with the accepted value for ‘g’.

Ticker tape being pulled through a ticker timer.

. . . . . . . . . . . . . . . A B C D E F G H I J K L