Physical Setting / Physics Regents Examinations: How to Answer Part C Questions

How to Answer Part C Questions
An extended-response question is an examination question that requires the test taker to do more than to choose among several responses or to fill in a blank. You may need to perform numerical calculations, draw and interpret graphs, and provide extended written responses to a question or problem.

Part C of the New York State Regents Examination in Physics contains free-response questions. 

Solving Problems Involving Numerical Calculations
To receive full credit you must:
Provide the appropriate equation(s).
Substitute values and units into the equation(s).
Display the answer, with appropriate units and to the correct number of significant figures.
If the answer is a vector quantity, include its direction.
Although SI units are used on the Regents examination, you are expected to have some familiarity with other metric units such as the gram and the kilometer.
You should write as legibly as possible. Teachers are human, and nothing irks them more than trying to decipher a careless, messy scrawl. It is also a good idea to identify your answer clearly, either by placing it in a box or by writing the word “answer” next to it.

Warning: If you provide the correct answer but do not show any work, you will not receive any credit for the problem!

The following is a sample problem and its model solution.

Problem
A 5.0-kilogram object has a velocity of 10 meters per second [east]. Calculate the momentum of this object.

Solution
p = mv
p = (5.0 kg)(10 m/s [east])
p = 50 kg.m/s [east]

Graphing Experimental Data
To receive full credit you must:
Label both axes with the appropriate variables and units.
Divide the axes so that the data ranges fill the graph as nearly as possible.
Plot all data points accurately.
Draw a best-fit line carefully with a straightedge. The line should pass through the origin only if the data warrant it.
If a part of the question requires that the slope be calculated, calculate the slope from the line, not from individual data points.
A graph should have a title, and the independent variable is usually drawn along the x-axis.

The following is a sample problem and its model solution.

Problem
The weights of various masses, measured on Planet X, are given in the table below.
 

Draw a graph that illustrates these data.
Use the graph to calculate the acceleration due to gravity on Planet X.

Solution
The graph shown below incorporates the essential items that were listed in the table.

Since the magnitude of the gravitational acceleration can be determined by calculating the ratio of weight to mass (g = W/m), we can calculate the value of g from the slope of the graph.

We choose two points on the line; we do not use the data points themselves:

 

Drawing Diagrams
To receive full credit you must:
Draw your diagrams neatly, and label them clearly.
Draw vectors to scale and in the correct direction. If you are given a scale, you must draw your vectors to that scale.
Bring a straightedge and a protractor with you so that you can draw neat, accurate diagrams.

Writing an Extended-Response Answer
To receive full credit you must:
Use complete, clear sentences that make sense to the reader.
Use correct physics in your explanations.

A sample question and acceptable and unacceptable answers are given below.

Question
A student draws a graph of the potential difference across a conductor versus the current in the conductor.How can the resistance of the conductor be determined from the graph the student has drawn?

Acceptable Answers
The resistance can be determined from the slope of the graph.
The change in the potential difference divided by the change in current determines the resistance of the conductor.
The slope of the straight line is the resistance of the conductor.

Unacceptable Answers
The slope. (Incomplete sentence)
The y-intercept of the graph determines the resistance.(Incorrect physics)