Science
Strand IV
Use Scientific Knowledge from the Physical Sciences in Real-World Contexts

 

Science/Strand IV
Content Standard 3
All students will describe how things around us move and explain why things move as they do; demonstrate and explain how we control the motions of objects; and relate motion to energy and energy conversions. (Motion of Objects)

 

Science/Strand IV/Content Standard 3
Middle School

 

Science/Strand IV/Content Standard 3/Middle School
Benchmark 3
Describe the non-contact forces exerted by magnets, electrically charged objects, and gravity.

Benchmark Clarification

Some forces are exerted from a distance with objects not touching. Examples of these forces are magnetic attraction or repulsion, attraction or repulsion between electric charges, and gravitational attraction.

These types of forces are called non-contact forces, because they occur between objects that don’t touch. These forces can be demonstrated by the following:

The magnetic poles of a magnet will either repel or attract other magnet poles of another magnet. For example, the north pole of one magnet will repel the north pole of the other magnet (same thing will occur with two south poles), but the north pole of one magnet will attract the south pole of the other magnet.

Electrically charged objects will either repel other electrically charged objects if their charges are alike, such as a positively charged object near another positively charged object, or will attract other electrically charged objects, such as if one object is charged positively and the other negatively. Unlike charges attract, like charges repel.

Gravity is an attractive force that occurs between any two objects that have mass. These objects are attracted to each other (Moon held in orbit by the Earth). The greater the mass of the object, the stronger the gravitational pull. Increased distance between objects results in decreased gravitational pull.

Students will:

  • Describe forces exerted from a distance with objects not touching.

See Forces and motion, (SCI.IV.3.MS.2).

See Weight and mass, (SCI.IV.1.MS.2).

See (SCI.V.4.MS.2).

Key Concept / Real World Context / Instructional Example / Assessment Example / Resources

 

Science/Strand IV/Content Standard 3/Middle School/Benchmark 3
Key Concept
Electrical charges and magnetic poles:

  • North Pole
  • South Pole
  • positive charge
  • negative charge
  • mass
  • weight
  • gravitational pull

Charging by rubbing or touching

Electrical attraction and repulsion

Force depends on size of charges or masses, and decreases quickly with distance

 

Science/Strand IV/Content Standard 3/Middle School/Benchmark 3
Real World Context
Electrically charged or polarized objects:

  • balloons rubbed on clothing
  • bits of paper
  • salt grains
  • static cling
  • magnets
  • magnetic materials
  • Earth’s gravitational pull on objects near its surface
  • Sun’s gravitational pull on solar system objects

 

Science/Strand IV/Content Standard 3/Middle School/Benchmark 3
Instructional Example

Benchmark Question: What are the non-contact forces involved with magnets, electrically charged objects, and gravity?

Focus Question: How do magnets interact?

The teacher will ask students, “Between two magnets, where do pushes and/or pulls occur?” Students will discuss possible answers and reasons for their answers. Each student will write a prediction of how close two magnets must be before one magnet moves. Each small group will measure how close one magnet must be to another before the other one moves (any movement counts) using two similar magnets (any kinds) and a ruler. Each group will follow these procedures:

  • Place a ruler flat on a desk.
  • Place one magnet at the end of the ruler (zero cm).
  • Place and slide a second magnet from the opposite end of the ruler until the first magnet moves (attracted or repelled).
  • Repeat, using different magnetic end combinations, N to N, N to S, S to S, S to N.

Students will record their data and write their conclusions. Each group will present its data and the teacher will construct a graph of class data.

Students should conclude that the movement will occur at the same distance no matter what combination of poles is used. When like pole combinations are used, a push occurs, and when unlike pole combinations are used, a pull occurs.

Constructing: (SCI.I.1.MS.1), (SCI.I.1.MS.3), (SCI.I.1.MS.4).

Reflecting: (SCI.II.1.MS.2).

 

Science/Strand IV/Content Standard 3/Middle School/Benchmark 3
Assessment Example

The teacher will give students several ring magnets and a pencil. Ask students, “What would happen if a student put two ring magnets on an upright pencil?”

Each student will write a prediction and then conduct the following investigation:.

1. Arrange various numbers of magnets and a pencil in various ways.

2. Draw and label observations.

3. Measure the spaces between the magnets.

4. Record data.

5. Write answers to the following questions based upon your observations:

a. What patterns do you see in the behavior of the magnets and the spaces between them?

b. What would happen if the pencil were not there?

c. Why does the magnet float (occurs when the force of repulsion is balanced with the weight of the object) when on one side and not the other side?

d. What happens to the spaces between the magnets as magnets are added?

e. How can you make the top magnet jump off the pencil?

f. What can you infer about magnets from this investigation?

(Give students rubric before activity.)

Scoring Rubric

Criteria

Apprentice

Basic

Meets

Exceeds

Correctness of answers

Answers fewer than two questions with some correct information.

Answers two to three questions correctly.

Answers all four questions correctly without contradictions.

Answers the four questions with complete responses and clear, coherent, unambiguous, and elegant explanations.

Accuracy of inference

Writes an inference with numerous inconsistencies and few consistencies.

Writes an inference that contains some consistencies.

Writes a complete and accurate inference.

Writes a complete and accurate inference based on past experimentation.

 

Science/Strand IV/Content Standard 3/Middle School/Benchmark 3
Resources

Webliography.
http://mtn.merit.edu/mcf/SCI.IV.3.MS.3.html

Mostly Magnets. AIMS.
http://wwws.aimsedu.org/aimscatalog/default.tpl

Magnetism. TOPS.
http://topscience.org/

Popping With Power. AIMS.
http://wwws.aimsedu.org/aimscatalog/default.tpl