Our first group project this homeschool year will be to build a marble roller coaster. If the track is wide enough they can also use a hot wheels car.
Simply speaking, a roller coaster is a machine that uses gravity and inertia to send a train of cars along a winding track. This combination of gravity and inertia, along with g-forces and centripetal acceleration give the body certain sensations as the coaster moves up, down, and around the track.
Vocabulary/Definitions
acceleration: How quickly an object speeds up, slows down or changes direction. Is equal to change in velocity divided by time.
critical velocity: The speed needed at the top of a loop for a car to make it through the loop without falling off the track.
force: Any push or pull.
friction: A force caused by rubbing between two objects.
g-force: Short for gravitational force. Is equal to the force exerted on an object by the Earth's gravity at sea level.
gravitational constant: The acceleration caused by the Earth's gravity at sea level. Is equal to 9.81 m/sec^2 (32.2 ft/sec^2).
gravity: A force that draws any two objects toward one another.
kinetic energy: The energy of an object in motion, which is directly related to its velocity and its mass.
potential energy: The energy stored by an object ready to be used. (In this lesson, we use gravitational potential energy, which is directly related to the height of an object and its mass.)
speed: How fast an object moves and is equal to the distance that object travels divided by the time it takes.
velocity: A combination of speed and the direction in which an object travels.
The kids will make the blueprints of their roller coaster. Do they want a loop? Will gravity alone be enough for the marble (or car) to complete the coaster? These are the things we need to think about while planning.
Roller coasters are entirely driven by the force of gravity. The excitement of a ride comes from the ongoing conversion between potential and kinetic energy, which we know from the law of conservation of energy. Friction is important to slowing down roller coaster cars and acceleration plays a role in the experience provided by roller coaster cars as they move along a track.
Materials:
The kids will look through the craft box to see if we have enough materials for their roller coaster. If we need anything extra, they need to make a list and we'll head to the store.
Some Variations
You probably have marbles of different diameters in your collection. What happens if you test marbles of different diameter on your roller coaster? Can they all loop the loop? If some marbles can't make it, can you figure out why?
You can expand the experiment by building a set of roller coaster tracks with various loop sizes. How does the height requirement change when the loop diameter increases? How does the height requirement change when the loop diameter decreases?
Maybe you noticed that your loop wobbles a bit as your marble passes through it. The energy to move the track comes from the marble. The energy that the marble loses to make the track move means less energy is available to make the marble itself move. Can you think of a way to stabilize the loop so that it doesn't wobble? With a stabilized loop, can the marble start at a lower height and still make it through the loop? Design an experiment to find out!
Try using different lengths of roller coaster track so that you can adjust the slope of the track leading to the loop. Keep the starting height the same, but change the slope by adding additional track length. (Remember, slope is rise/run, so you'll be holding the "rise" constant, and gradually increasing the "run.") Do you think that the marbles will continue to "loop the loop" as the slope is decreased? Tip: start with a track height and loop diameter such that the marbles just make it around the loop.
Simply speaking, a roller coaster is a machine that uses gravity and inertia to send a train of cars along a winding track. This combination of gravity and inertia, along with g-forces and centripetal acceleration give the body certain sensations as the coaster moves up, down, and around the track.
Vocabulary/Definitions
acceleration: How quickly an object speeds up, slows down or changes direction. Is equal to change in velocity divided by time.
critical velocity: The speed needed at the top of a loop for a car to make it through the loop without falling off the track.
force: Any push or pull.
friction: A force caused by rubbing between two objects.
g-force: Short for gravitational force. Is equal to the force exerted on an object by the Earth's gravity at sea level.
gravitational constant: The acceleration caused by the Earth's gravity at sea level. Is equal to 9.81 m/sec^2 (32.2 ft/sec^2).
gravity: A force that draws any two objects toward one another.
kinetic energy: The energy of an object in motion, which is directly related to its velocity and its mass.
potential energy: The energy stored by an object ready to be used. (In this lesson, we use gravitational potential energy, which is directly related to the height of an object and its mass.)
speed: How fast an object moves and is equal to the distance that object travels divided by the time it takes.
velocity: A combination of speed and the direction in which an object travels.
The kids will make the blueprints of their roller coaster. Do they want a loop? Will gravity alone be enough for the marble (or car) to complete the coaster? These are the things we need to think about while planning.
- The top of the first hill must be the highest point on the roller coaster.
- Cars move fastest at the bottoms of hills and slowest at the tops of hills.
- Friction converts useful energy into heat and must be minimized.
- G-forces greater than 1 occur at the bottoms of hills.
- G-forces less than 1 occur at the tops of hills.
- To avoid falling, cars must have a certain velocity at the tops of loops.)
Roller coasters are entirely driven by the force of gravity. The excitement of a ride comes from the ongoing conversion between potential and kinetic energy, which we know from the law of conservation of energy. Friction is important to slowing down roller coaster cars and acceleration plays a role in the experience provided by roller coaster cars as they move along a track.
Materials:
The kids will look through the craft box to see if we have enough materials for their roller coaster. If we need anything extra, they need to make a list and we'll head to the store.
Some Variations
You probably have marbles of different diameters in your collection. What happens if you test marbles of different diameter on your roller coaster? Can they all loop the loop? If some marbles can't make it, can you figure out why?
You can expand the experiment by building a set of roller coaster tracks with various loop sizes. How does the height requirement change when the loop diameter increases? How does the height requirement change when the loop diameter decreases?
Maybe you noticed that your loop wobbles a bit as your marble passes through it. The energy to move the track comes from the marble. The energy that the marble loses to make the track move means less energy is available to make the marble itself move. Can you think of a way to stabilize the loop so that it doesn't wobble? With a stabilized loop, can the marble start at a lower height and still make it through the loop? Design an experiment to find out!
Try using different lengths of roller coaster track so that you can adjust the slope of the track leading to the loop. Keep the starting height the same, but change the slope by adding additional track length. (Remember, slope is rise/run, so you'll be holding the "rise" constant, and gradually increasing the "run.") Do you think that the marbles will continue to "loop the loop" as the slope is decreased? Tip: start with a track height and loop diameter such that the marbles just make it around the loop.
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