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TE Activity: Ramp and Review

In this hands-on activity — rolling a ball down an incline and having it collide into a cup — the concepts of mechanical energy, work and power, momentum, and friction are all demonstrated. During the activity, students take measurements and use equations that describe these energy of motion concepts to calculate unknown variables, and review the relationships between these concepts.

Light rail trains are a modern form of public transportation powered by overhead electrical lines that travel along dedicated pathway of steel rails. To design these trains to be quiet, efficient and safe, engineers considered all of the energy of motion concepts: the work required to convert the mechanical energy when the train went from a stopped position to forward/backward motion, how much momentum the train acquires between stations, and the power required to overcome the friction between the train's wheels and the effects of drag.

Learning Objectives
Materials
Introduction/Motivation
Procedure
Attachments
Troubleshooting Tips
Assessment
Extensions
Activity Scaling

Grade Level: 7 (6-8)	Group Size: 3
Time Required: 60 minutes	Activity Dependency : None
Expendable Cost Per Group : US$ 7
Keywords: energy, friction, kinetic energy, Joule, mechanical energy, momentum, potential energy, power, work

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Colorado Math
- 1. represent, describe, and analyze patterns and relationships using tables, graphs, verbal rules, and standard algebraic notation; (Grades 5 - 8) [2005]
- 1. demonstrate meanings for integers, rational numbers, percents, exponents, square roots, and pi (π) use physical materials and technology in problem-solving situations; (Grades 5 - 8) [2005]
- 1. estimate, use, and describe measures of distance, perimeter, area, volume, capacity, weight, mass, and angle comparison; (Grades 5 - 8) [2005]
- 2. construct, use, and explain procedures to compute and estimate with whole numbers, fractions, decimals, and integers; (Grades 5 - 8) [2005]
Colorado Science
- Standard 1: Students understand the processes of scientific investigation and design, conduct, communicate about, and evaluate such investigations. (Grades 0 - 12) [1995]
- Standard 6: Students understand that science involves a particular way of knowing and understand common connections among scientific disciplines. (Grades 0 - 12) [1995]
- 2.2 Students know that energy appears in different forms, and can move (be transferred) and change (be transformed). (Grades 0 - 12) [1995]
- 2.3 Students understand that interactions can produce changes in a system, although the total quantities of matter and energy remain unchanged. (Grades 0 - 12) [1995]

After this activity, students should be able to:

Identify components of mechanical energy, work and power, momentum, and friction and how they interrelate.
Construct a model to demonstrate potential and kinetic energy, work, power, momentum and friction.
Understand that energy, momentum, power and work, and friction can be described by equations.
Use multiple equations to solve for unknown variables.
Calculate the amount of mechanical energy, momentum, power and work, and friction in a system.

Before the Activity

Gather materials, including a copy of the Ramp and Review Worksheet for each group
You may want to set up a demo test station to help students visualize how the pieces go together.

With the Students

In this illustration of the activity setup, a golf ball is placed at the top of an angled yardstick with rails on the sides to guide it as it rolls down the ramp. A cup is placed at the bottom of the yardstick to catch the ball. Rails are also used to guide the cup as it slides away from the bottom of the yardstick due to the force of the rolling ball.

Activity set-up. The height, h, is the vertical distance from the ground to the top of the angled yardstick. The distance, d, is the horizontal distance from the bottom of the ramp to the point where the cup containing the ball comes to a rest.
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Pass out the materials to students in groups of three. (Teams of two or four also work).
Tape a dowel rod to each side of a yardstick, approximately 1-inch apart from each other. This serves as a track for the golf ball to roll down.
Prop the yardstick against a wall or desk to create a slope for the ball to roll down.
Place a small amount of crushed paper towels or tissues inside the cup to absorb the impact of the ball and keep the ball in the cup.
Place the cup at the end of the yardstick ramp to catch the ball at the end of the incline.
Tape the other two dowel rods a few inches apart to create a track for the cup to slide along.
On the Ramp and Review Worksheet, complete questions 1 and 2 (measure the height of yardstick and weight of golf ball).
Place the ball at the top of the ramp and let it go.
Measure the distance the cup travels at the end of the ramp and record that for question 3 on the worksheet.
Complete the calculations on the worksheet.

Pre-Activity Assessment

Brainstorming: Have the students to engage in open discussion. Remind students that no idea or suggestion is "silly." All ideas should be respectfully heard. Ask the students to think of situations that involve a combination of mechanical energy, momentum and collisions, work and power, and friction. (Example answer: Going down a slide. Potential energy turns into kinetic energy. Friction from sliding. As you gain velocity, you gain momentum.)

Activity Embedded Assessment

Worksheet: Have the students record measurements and follow along with the activity on their worksheet. After student teams have finished their worksheet, have them compare answers with their peers.

Hypothesize: Ask each group what would happen if a heavier glass cup was used instead of a lightweight cup. (Answer: The heavier cup would slow the overall speed of the ball and cup to conserve momentum. Since the lightweight cup is used, the ball and cup will barely slow down to conserve momentum.)

Post-Activity Assessment

Worksheet Discussion: Review and discuss worksheet answers with the entire class. Use the answers to gauge students' mastery of the subject.

Discussion Questions: Solicit, integrate and summarize student responses to these questions, which refer to question 8 on the Ramp and Review Worksheet:

Why is the work expressed as a negative value? (Answer: Work is defined as "force acting over a distance." When the force and distance traveled are in the same direction, the value of work is positive. However, in this case of friction, the force is acting in the opposite direction of the sliding cup, hence a negative value of work.)
How did the friction, momentum, kinetic and potential energy, and work and power all come together to make the cup move? How does this relate to activities you do every day? (Answer: To make the cup move, first we needed to build up momentum. This was done by giving the ball potential energy and converting it into kinetic energy. When the ball reached the bottom of the track, it collided with the cup and conserved momentum. Once the cup started sliding, friction came into play to bring the cup to a stop. The power of friction was related to how fast the cup stopped. This is very similar to riding down a hill with your scooter and braking to come to a stop.)

There is another form of mechanical energy called rotational energy that has not been discussed in this unit. In actuality, as the ball rolls down the incline, some of the potential energy is turned into rotational energy, while the rest is turned into kinetic energy. This decreases the balls velocity as it rolls down the incline and makes our calculated value of velocity slightly higher than it really is. Have your students search the Internet to find out more about rotational energy and why it causes certain objects to roll slower down an incline. A good Internet source at Wikipedia (a free, on-line encyclopedia): http://en.wikipedia.org/wiki/Rotational_energy.

For lower grades, have the students complete at least one trial of how far the cup slides and record that as their distance (question 3) on the Ramp and Review Worksheet. Also, you may want to run through the equations (found on the bottom of the worksheet) in front of the class. Question 6 on the worksheet may be difficult, so solve it together as a class.
For upper grades, have the students solve for velocity using the kinetic energy equation on their own. For example,

K.E. = ½ ∙ m ∙ V² → Velocity equals the square root of two times kinetic energy all divided by mass.

Integrated Teaching and Learning Program, College of Engineering, University of Colorado at Boulder Chris Yakacki, Malinda Schaefer Zarske, Denise Carlson © 2004 by Regents of the University of Colorado
The contents of this digital library curriculum were developed under a grant from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and National Science Foundation GK-12 grant no. 0226322. However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.

Last Modified: April 23, 2007