Ib Lab - 06 Vectors (dcp)

International Baccalaureate Physics

4/PSOW

Vectors Aim: • To use vector addition to calculate the mass of an unknown object. • To gain an understanding of balanced forces in situations of static equilibrium when two or more forces act at a point in a system.

IB Criteria Assessed Data Collection, Data Processing, Evaluation Criteria assessed

Equipment: 2 pulleys mounted on a board, thread, slotted masses, 3 sheets of white paper for each student. Method: 1. Set up the apparatus as shown in the diagram 2. Hang the unknown mass and two slotted masses from the 3 threads and let the system come to equilibrium. 3. Displace it several times and notice the variation in the position of the point O. 4. When the system comes to rest in an approximately mean position, accurately mark the position of point O and the directions of the 3 forces on a piece of white paper fixed to the board. 5. Label the point of intersection of the 3 force vectors as O. 6. Repeat the above procedure for two more systems by changing the magnitude of coplanar forces acting on the body. 7. Record the value of forces A and B for each system.

Aspect 1

2

3

Level awarded

Pl (a) Pl (b) DC DPP CE

Diagram:

O

A

B

C

Data Collection: Attach your three A4 sheets which clearly show the original data obtained. Data Processing and Presentation: 1. Using a suitable technique, determine the vector sum A+B and hence calculate the mass of the unknown object. 2. Compare this sum with the value of C obtained by measuring the unknown mass with a balance. 3. Include any uncertainties (both magnitude and direction).

© 2006 - Mike Dickinson

A

B

α β O C

8356921.doc

International Baccalaureate Physics

4/PSOW

Internal Assessment Marking Form Crit.

Pl(a)

Pl(b)

DC

DPP

CE

Aspects Research Question: Hypothesis: Variables: c. Identifies a focused c. Relates the hypothesis or c. Selects the problem or research prediction directly to the relevant question. research question and independent p. States the problem or explains it, quantitatively and controlled research question, but it where appropriate. variable(s). is unclear or incomplete. p. States the hypothesis or p. Selects some n. Does not state the prediction but does not relevant problem or research explain it. variables. question or repeats the n. Does not state a n. Does not select general aim provided by hypothesis or prediction. any relevant the teacher. variables. Materials / Control of Variables: Collecting Data: Apparatus: c. Describes a method c. Describes a method that c. Selects appropriate that allows for the allows for the collection apparatus or control of the of sufficient relevant materials. variables. data. p. Selects some p. Describes a method p. Describes a method that appropriate that makes some allows for the collection apparatus or attempt to control the of insufficient relevant materials. variables. data. n. Does not select n. Describes a method n. Describes a method that any apparatus or that does not allow for does not allow any materials. the control of the relevant data to be variables. collected. Collecting / Recording Raw Data: Organising / Presenting Raw c. Records appropriate raw data (qualitative Data: and/or quantitative), including units and c. Presents raw data clearly, uncertainties where necessary. allowing for easy p. Records some appropriate raw data. interpretation. n. Does not record any appropriate raw data. p. Presents raw data but does not Aspect 1 includes units, uncertainties, allow for easy interpretation. significant digits n. Does not present raw data or presents it incomprehensibly. Processing Raw Data: Presenting Processed Data: c. Processes the raw c. Presents processed data appropriately, helping data correctly. interpretation and, where relevant, takes into p. Some raw data is account errors and uncertainties. processed correctly. p. Presents processed data appropriately but with some n. No processing of raw errors and/or omissions. data is carried out or n. Presents processed data inappropriately or major errors are made incomprehensibly in processing. Aspect 2 includes uncertainty bars, max / min slopes (HL), axes with labels and units, best fit line drawn Drawing Conclusions: Evaluating procedure(s) Improving the c. Gives a valid and results: investigation: conclusion, based on the c. Evaluates procedure(s) c. Identifies correct interpretation of and results including weaknesses and the results, with an limitations, states realistic explanation and, where weaknesses or errors. suggestions to appropriate, compares p. Evaluates procedure(s) improve the results with literature and results but misses investigation. values. some obvious p. Suggests only p. States a conclusion that limitations or errors. simplistic has some validity. n. The evaluation is improvements. n. Draws a conclusion that superficial or n. Suggests unrealistic

© 2006 - Mike Dickinson

Level ccc 3 ccp 2 ccn 2 cpp 2 ppp 1 cpn 1 cnn 1 ppn 1 pnn 0 nnn 0

Grade

ccc 3 ccp 2 ccn 2 cpp 2 ppp 1 cpn 1 cnn 1 ppn 1 pnn 0 nnn 0

cc 3 cp 2 cn 1 pp 1 pn 0 nn 0

cc 3 cp 2 cn 1 pp 1 pn 0 nn 0

ccc 3 ccp 2 ccn 2 cpp 2 ppp 1 cpn 1 cnn 1 ppn 1 pnn 0 nnn 0

8356921.doc

International Baccalaureate Physics

misinterprets the results.

© 2006 - Mike Dickinson

4/PSOW

irrelevant.

improvements.

8356921.doc