Mechanical Energy

Mechanical Energy It’s finally here; the day you’ve been waiting for – your class trip to Carowinds. As you step in to the cart for Fury 325, your palms are sweaty. The cart slowly makes its way to the chain that pulls you up the 325 foot lift-hill. Your heart is beating faster as you look down and see the cars in the parking lot that look like multi-colored jelly beans. You say to your friend, “I really hope this thing doesn’t fall off the track.” As you reach the top of the hill, you start to scream – both from excitement and fear. The last thing on your mind is science. But, without science, your ride would be over before it even began. Energy All roller coasters, including Fury 325, utilize energy to bring fun and fear to their riders. Energy is the ability to do work. (Work is calculated by force x distance, but that’s for another day.) There are several types of energy. One type of energy that is very important to roller coasters is mechanical energy. Mechanical Energy is the energy associated with the motion and the position of an object. Anything that is moving, or could move, has mechanical energy. Roller coasters, cars, basketballs – all of these have mechanical energy. Mechanical energy is calculated by adding the potential energy of an object with the kinetic energy. Potential Energy Potential energy is the energy an object has because of its position, instead of its motion. Potential energy is often referred to as “stored energy.” The potential energy from gravity changes depending on two variables – height and mass. As height increases, so does potential energy. Likewise, if mass increases, potential energy does, too. When you are waiting for the ride on Fury 325 to begin, you are at the bottom of the hill, so you do not have very much potential energy. As more and more people get into the roller coaster car, the potential energy increases because mass increases. As the roller coaster starts to climbs the hill, the potential energy increases again. The potential energy reaches its maximum point when the roller coaster makes it to the top of the hill. At this point, you begin your descent down the first hill. This is where the potential energy transforms into kinetic energy. Kinetic Energy Kinetic energy is the energy that an object has due to its motion. Kinetic energy occurs when an object actually moves. Kinetic energy depends on two variables – mass and velocity. If an object has more mass, it will have more kinetic energy. Also, if it is traveling at a greater velocity, it will have more kinetic energy. When you finally reach the top of the first hill on Fury 325, the roller coaster slowly begins going downhill. While going down the hill, the roller coaster picks up more and more speed. The potential energy the cart had at the top of the hill transforms into kinetic energy at the bottom of the hill. Because you are moving so fast, you have a very high kinetic energy, and a very low potential energy. Throughout the rest of the ride, you will go up and down multiple hills. The potential energy that was put into the roller coaster from the very first hill, and the kinetic energy on the very first drop, provide enough energy for you to continue to go through the rest of the roller coaster without any other assistance. The cart has so much inertia that it will travel all the way to the end of the track without stopping. It’s hard to think about energy when you are 325 feet off the ground, getting ready to zoom down an 85-degree hill. Without mechanical, potential, and kinetic energy, though, your ride would be pretty boring. Part 1: Definitions Energy is the capacity to do work or produce heat. It exists in various forms and is essential for all physical processes 1. Energy: ____________________________________________________________________ Mechanical energy is the sum of kinetic energy and potential energy associated with the motion and position of an object system. It includes both the energy of motion (kinetic energy) and the energy stored in position (potential energy) 2. Mechanical Energy: or___________________________________________________________ Potential energy is the energy that an object possesses due to its position or configuration within a force field or due to its condition. It is the energy that is stored and available for use, such as gravitational potential energy or elastic potential energy 3. Potential Energy: ____________________________________________________________ Kinetic energy is the energy that an object possesses due to its motion. It depends on the mass of the object and its 4. Kinetic Energy: ______________________________________________________________ velocity and is directly proportional to both. Kinetic energy can be transferred between objects and converted into other forms of energy Part 2: Comprehension summing the kinetic energy and potential energy of an object or system. 1. How is mechanical energy calculated? __________________________________________ Potential energy depends on the object's position or configuration within 2. What two things does potential energy depend on? ________________________________ a force field and its condition 3. Name two different ways that potential energy will change as you ride a roller coaster. ____ It increases as the coaster climbs to the top of a hill due to gaining height and gravitational potential energy. It____________________________________________________________________________ decreases as the coaster descends from a hill due to losing height and converting potential energy into kinetic energy. 4. When at the top of a roller coaster, as it begins to go down the first drop, what happens to At the top of a roller coaster, as it begins to go down the first drop, the potential energy decreases. the potential energy? ___________________________________________________________ ______________________________________________________________________________ 5. How is kinetic energy different than potential energy? ________________________________ Kinetic energy is the energy an object possesses due to its motion, while potential energy is the energy an object possesses due to its position or condition. ______________________________________________________________________________ 6. What variables does the amount of kinetic energy depend on? ________________________ The amount of kinetic energy depends on the mass of the object and its velocity. ______________________________________________________________________________ 7. How does the kinetic energy at the top of the first hill compare to the kinetic energy at the The kinetic energy at the top of the first hill is typically lower than the kinetic energy at the bottom of the first hill because the coaster gains bottom of the first hill? ___________________________________________________________ speed as it descends. 8. How does the potential energy at the top of the first hill compare to the potential energy at the bottom of the first hill? _______________________________________________________ 9. Why doesn’t a roller coaster stop as it travels through the rest of the coaster, even though A roller coaster doesn't stop as it travels through the rest of the track because of the conservation of mechanical there is nothing else powering it? ___________________________________________________ energy. The initial potential energy at the start of the ride is converted into kinetic energy as the coaster descends, ______________________________________________________________________________ The potential energy at the top of the first hill is typically higher than the potential energy at the bottom of the first hill because the coaster gains height as it ascends. and this kinetic energy is conserved throughout the ride, allowing the coaster to continue moving even without external power sources. friction and air resistance gradually reduce the coaster's kinetic energy, but it still has enough energy to complete the ride. Part 4: Practice Test Questions 1. A high diver steps off a diving platform that is 10 meters above the water. If no air resistance is present, during the fall there will be a decrease in the diver’s a. potential energy b. kinetic energy c. mechanical energy d. momentum 2. As a heavy metal ball rolls down a hill it goes faster and faster. Which statement is true? a. The ball’s potential energy is changing to kinetic energy. b. The ball is gaining potential energy from the hill. c. The ball is rapidly losing kinetic energy as it rolls down the hill. d. The ball will continue gaining kinetic energy until it stops. 3. A skateboarder travels from location 1 to location 4 as shown below. At which location does the skateboard have the most kinetic energy and the least potential energy? a. 1 b. 2 c. 3 d. 4