ROLLER COASTERS By: Dr. Curtis Varnell, WAESC Web sites for additional information: http://www.funderstanding.com/k12/coaster/ http://www.learner.org/interactives/parkphysics/coaster.html Rollercoaster.com http://www.learner.org/interactives/parkphysics/coaster.html http://science.howstuffworks.com/roller-coaster2.htm Roller coasters developed in the United States in the late 1800’s and became popular throughout the country by the “roaring twenties.” In 1955, Disneyland was built as the first theme park. Disney introduced the Matterhorn, the first tubular steel roller coaster. Up until this time, coasters were built out of wood, which limited the way loops could be handled. The loops, a corkscrew track, and stability and other exciting developments became practical as a result of this change. The first successful inverted coaster was introduced in 1992. This allows riders to dangle their feet freely below them as the ride. In 1997, Six Flags Magic Mountain designed a roller coaster that reaches heights of 415 feet and can reach speeds of 100 miles per hour. Other amusement parks soon followed and now these machines can be found at Six Flags over Texas, Disney World and other locations. All of us have our favorite roller coasters and are favorite amusement parks to visit. What does the future hold? Only imagination and the laws of physics can determine that. What causes a roller coaster to work? Several forces work together to make your ride exciting and successful. The car is pulled to the top of the first hill at the beginning of the ride, but after that the coaster must complete the ride on its own. You aren't being propelled around the track by a motor or pulled by a hitch. The conversion of potential energy to kinetic energy is what drives the roller coaster, and all of the kinetic energy you need for the ride is present once the coaster descends the first hill. The coaster builds up a reservoir of potential energy as it is pulled up to the top of the ride. Potential energy is often referred to as energy of position. As the coaster gets higher in the air, gravity can pull it down a greater distance. You experience this when your ride a bike, drive a car, or sled down from the top of a hill. You increase potential energy as you go up the hill and than release it as kinetic energy (the energy of motion) as you go down the hill. Once you start cruising down that first hill, gravity takes over and all the built-up potential energy changes to kinetic energy. Gravity applies a constant downward force on the cars. When you reach the bottom of the first hill, excess energy us used to carry you up the next hill. Friction is a force that opposes motion. You experience this when your bike slows as you stop peddling or your parent’s car stops when brakes apply great friction and cause kinetic energy to be used up. Heat is generated when this occurs. Roller coasters reduce friction by using different kinds of wheels to make the ride smoother. The tracks on the roller coaster control the way and direction the car falls. If the tracks slope down, gravity pulls the front of the car toward the ground, so it accelerates. If the tracks tilt up, gravity applies a downward force on the back of the coaster, so it decelerates Sir Isaac Newton’s first Law of Motion states that an object in motion tends to stay in motion. The roller coaster car will maintain a forward velocity even when it is moving up the track, opposite the force of gravity. When the coaster reaches the top of one of the smaller hills that follows the initial lift hill, its kinetic energy changes back to potential energy. In this way, the course of the track is constantly converting energy from kinetic to potential and back again. This change of energy results in changes in acceleration which is what makes roller coasters so much fun. Most roller coasters have hills that decrease in height as you move along the track. This is necessary because the total energy reservoir built up in the lift hill is gradually lost to friction between the train and the track, as well as between the train and the air. Have you heard the “whoosh” sound when your coaster ride is complete? This is caused by compressed air that acts as a brake and increases friction to bring your ride to a stop. Vocabulary: Potential Energy Kinetic Energy Sir Isaac Newton First Law of Motion Acceleration gravity Mass friction Standards: N.S. Inquiry and Process Skills, grades K-4: measurement, interpret evidence, develop hypothesis, generate conclusion. N.S. Scientific Equipment and Technology, Grades K-4: use of rulers, stop watches, graphs, calculators. P.S. Motion and Forces, Grades K-4: Force, direction, motion, mass, gravity. Grade 5-8: potential and kinetic energy, Newton’s law of motion, applying Newton’s law to the real world, compare mass and weight, gravitational forces, friction, effect of forces, simple machines and motion. Objectives: The student will accurately define potential and kinetic energy. The student will understand the effects of weight and speed on momentum. The student will explain the relationship of height and potential energy to the resulting kinetic energy produced. Time: One to two class periods Materials needed per group of three or four students: 10 foot of clear one quarter inch vinyl tubing (Lowe’s or Sutherland’s) 3-4 BB’s per group (can vary with other materials of the same diameter but different mass) Meter stick for each group Masking tape to hold the tubing into place Stop watch if you wish to measure speed. Procedure: Divide the class into groups of 3 to 5 students. Each group will need the supplies listed above. Use the height of the student’s desk as the first hill (about 4 ft.). Attach the tubing level with the desk top by using masking tape. Have the students to set the tubing at a 45 degree angle with the floor and with no loops and determine the speed the BB travels to the end of the tube by dropping the BB into the tube and measuring the time it takes for it to exit the end of the tube. Speed is equal to distance (10 ft.) divided by time and the answer should be in ft. per second. Allow the students to vary the angle and see how this influences speed of the roller coaster (BB). Students should record three trial runs. Students should design a roller coaster with three total hills. The first hill is the desk and they must add two more hills that follow and the BB must travel through the entire length. The student group with the greatest total inches of height in the three combined hills wins the class contest. Allow each group to record time required for the BB to travel thought their roller coaster. Extensions: As the students work together, they can try to put side motion or loops in the tubing to see the affect this has on the roller coaster BB. As the height and angles of the roller coaster are changed the groups will realize the effects that each design has on the roller coaster. If possible, find other materials that have greater and less density than the BB to test the changes in mass of the roller coaster. Check out the web sites above and project the roller coaster activity onto your smart board or through your digital projector. Students can vary mass, height, etc. of the digital roller coaster and compare it to what they have observed. Student Handouts Vocabulary you need to know: Potential Energy Kinetic Energy Sir Isaac Newton First Law of Motion Acceleration gravity Mass friction Instructions: Your group is to design and name your very own roller coaster. It must have a minimum of three loops. Attach the tubing level with your desk top by using masking tape. You should set your coaster frame (tubing) at no greater angle than 45 degrees. Your teacher will assist you in doing this if you have need assistance. Drop the roller coaster (BB) into the tube and measure how many seconds it takes to travel to the end of your coaster. Your coaster is 10 ft. long. To determine the speed your coaster is traveling, divide 10 feet by how many seconds it took to reach the end of the coaster. You can use a calculator. Speed is equal to distance (10 ft.) divided by time and the answer should be in feet per second. You can change your angle to see if this affects your roller coasters speed. Record three trial runs in the space below. Roller Coaster Name______________________________________________________ Trial Run 1 Trial Run 2 Trial Run 3 Distance 10 ft. 10 ft. 10 ft. Time Speed (S= d/t) angle How did changing the angle affect your speed? Each group should design a roller coaster with three total hills. The first hill is the desk and you must add two more hills that follow. The roller coaster must travel through the entire length. The student group with the greatest total inches of height in the three combined hills wins the class contest. Try Allow each group to record time required for the BB to travel thought their roller coaster. Record the time required for your roller coaster to travel the entire length. Hill one Hill two Hill three Total (cm) Time Experiment by adding twists, rolls, and loops to your roller coaster. How do these affect your roller coaster?