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 2
Relate motion of objects to unbalanced forces in two dimension.

Benchmark Clarification

Motion can be described in terms of balanced and unbalanced forces.

Examples of balanced forces: When an object sits motionless on a table, the forces acting on the object are balanced. The force of the object on the table (action) is equal to the force of the table pushing up on the object (reaction). When a car travels at a constant speed, the forward force of the car is equal to the frictional forces acting on the car.

Examples of unbalanced forces: When a car speeds up, the forces are unbalanced because the forward force acting on the car is greater than the frictional forces pushing back on the car.

Students will:

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

 

Science/Strand IV/Content Standard 3/Middle School/Benchmark 2
Key Concept
Changes in motion and common forces:

  • speeding up
  • slowing down
  • turning
  • pushing
  • pulling
  • friction
  • gravity
  • magnets

Additional forces:

  • attraction
  • repulsion
  • action/reaction pair (interaction force)
  • buoyant force
  •  

Size of change is related to strength of unbalanced force and mass of object

 

Science/Strand IV/Content Standard 3/Middle School/Benchmark 2
Real World Context
Changing the direction:

  • changing the direction of a billiard ball
  • bus turning a corner

Changing the speed:

  • car speeding up
  • a rolling ball slowing down
  • magnets changing the motion of objects
  • walking
  • swimming
  • jumping
  • rocket motion
  • objects resting on a table
  • tug-of-war

 

Science/Strand IV/Content Standard 3/Middle School/Benchmark 2
Instructional Example

Benchmark Question: How do forces affect the motion of an object?

Focus Question: How can the motion of objects be affected by balanced and unbalanced forces?

Each student will thread a string at least five meters long through a drinking straw and tie the string between two chairs that are set at least four meters apart so that the string is taut. The teacher will inflate the balloon (“hotdog” type balloons work best) and twist and hold the end to keep it inflated (do not tie). The teacher will attach the balloon with tape to the drinking straw with the twisted end closest to one chair. When releasing the balloon, the teacher will ask students, “What started the balloon moving?” and “What happened as the balloon was released?” Using the terms “balanced” and “unbalanced forces,” students will explain the motion of the balloon. Discussion should include the terms found in the Key Concepts.

Students should be able to set up their own investigations and write formal lab reports for the second activity. The teacher will give each small group a wooden block with a sturdy eye hook on two opposite ends, two spring scales, and a flat surface to work on. Students will design and carry out an investigation to determine the effects of balanced and unbalanced forces on the motion of the block. Students will record data. Each student will write a lab report describing the investigation. Each student will discuss their results using the terms in the Key Concepts.

Students should have access to reference materials that could assist them in their investigation design (e.g., encyclopedias, science textbooks, etc.).

Constructing: (SCI.I.1.MS.1), (SCI.I.1.MS.2), (SCI.I.1.MS.3), (SCI.I.1.MS.4), (SCI.I.1.MS.5), (SCI.I.1.MS.6).

Reflecting: (SCI.II.1.MS.2), (SCI.II.1.MS.3).

 

Science/Strand IV/Content Standard 3/Middle School/Benchmark 2
Assessment Example

Each student will draw a picture of two teams of students playing tug-of-war. Using the words “balanced forces,” “unbalanced forces,” and “motion,” each student will write an explanation of what happens when the tug-of-war teams both pull away from each other but there is no movement. Students should use arrows on the diagram to represent the forces of both teams. The stronger force should be represented by a larger arrow. Using the words “balanced forces,” “unbalanced forces,” and “motion,” each student will write an explanation of what needs to happen for one team to be the winner of the tug-of-war.

(Give students rubric before activity.)

Scoring Rubric

Criteria

Apprentice

Basic

Meets

Exceeds

Accuracy of description-forces in no movement situation

Identifies no balanced forces and incorrectly or incompletely draws force arrows on diagram.

Identifies both of the balanced forces and incorrectly or incompletely draws force arrows on diagram.

Identifies both balanced forces and correctly draws force arrows on diagram.

Provides clear and complete identification of balanced forces and correctly draws force arrows on diagram.

Accuracy of description-forces in winning situation

Identifies none of the unbalanced forces and incorrectly or incompletely draws force arrow on diagram.

Identifies both of the unbalanced forces and incorrectly or incompletely draws force arrow on diagram.

Identifies both of the unbalanced forces and correctly draws force arrow on diagram.

Provides clear and complete identification of unbalanced forces and correctly draws force arrow on diagram.

 

Science/Strand IV/Content Standard 3/Middle School/Benchmark 2
Resources

Webliography.
http://mtn.merit.edu/mcf/SCI.IV.3.MS.2.html

Taylor, Beverley. Teaching Physics with Toys: Activities for Grades K-9. McGraw-Hill, 1995.