Description:

Students investigate the common observation that your body gets pushed against the side of a car when the vehicle makes turns. The students look at objects that move in circles to see what keeps them moving in a circle. This exercise demonstrates three ideas about circular motion. 1) Forces are needed to cause circular motion; 2) When a force causing an object to move with circular motion stops, the object will move with straight line motion tangent to the circle; 3) Objects moving straight will continue to move straight until an outside force causes them to turn.

This task is designed to take students approximately 40-50 minutes to complete.

Overall Task Content Area:

Physical Science

Specific Knowledge Areas:

Motion and forces

Performance Expectations:

• conducting investigations
• using equipment
• gathering, organizing, and representing data
• formulating conclusions from investigational data
• applying scientific principles to develop explanations and solve new problems

National Science Education Standards:

8 B PS 2: Motions and forces: Grades 5-8
2.1  The motion of an object can be described by its position, direction of motion, and speed. That motion can be measured and represented on a graph.

2.2  An object that is not being subjected to a force will continue to move at a constant speed and in a straight line.

8 A SI 1: Abilities necessary to do scientific inquiry: Grades 5-8

1.4 Develop descriptions, explanations, predictions, and models using evidence. Students should base their explanation on what they observed, and as they develop cognitive skills, they should be able to differentiate explanation from description — providing causes for effects and establishing relationships based on evidence and logical argument. This standards requires a subject knowledge base so the students can effectively conduct investigations, because developing explanations establishes connections between the content of science and the contexts within which students develop new knowledge.

1.5 Think critically and logically to make the relationships between evidence and explanations. Thinking critically about evidence includes deciding what evidence should be used and accounting for anomalous data. Specifically, students should be able to review data from a simple experiment, summarize the data, and form a logical argument about the cause-and-effect relationships in the experiment. Students should begin to state some explanations in terms of the relationship between two or more variables.

(Use the "hot" link on the PALS home page to check the full text of related National Science Education Standards, if desired.)

National Council of Teachers of Mathematics:

Problem Solving (PS2): Solve problems that arise in mathematics and in other contexts.

General Instructions to the Teacher:

This task is designed to take students approximately 40-50 minutes to complete.

Students will be working in groups of 4-6 for one portion of the experiment/activity part of this exercise and will finish the group portion working in pairs. Allow approximately 20 to 25 minutes for the group activity portion of the exercise and an approximately equal time period for students to complete the individual portion.

Students should be ready to work as soon as the period begins. Group assignments should be made in advance. The materials should be set out at each lab station, if possible. A central supply area, if needed, should be accessible. All supplies should be clearly labeled.

Materials for "Circular Motion":

Each working group should have:

• 1 paper/plastic plate with outside ridge and no compartments
• one 9/16" marble
• ruler with ridge down the center
• tennis ball
• plastic bag
• string (1 meter per group)
• scissors
• tape
• 1 pen or pencil per student

Special Directions for Teacher Setup:

For part two of the exercise, students will need to work in pairs. You will need to have a large open space for part two. The gymnasium or outside on a field or playground would be best.

Safety:

• Be careful.
• Teachers and students should always exercise appropriate safety precautions and utilize appropriate laboratory safety procedures and equipment when working on science performance tasks.