The Second Task
My same STEM group from Fire Away, Nico, Wesley, and I, had a second task. This time, we had to design a car that can carry two rolls of 50 pennies (total of 100 pennies) a distance of 5 meters. We decided on using rubber bands to launch a box containing the pennies.
The Presentation
The Final Product
My group successfully created a working car that could move 5 meters. The car took 2.3s to travel 5m and had a peak velocity of 3.3 m/s. Its rubber bands were 1.67m and the car's mass is 1.3 kg. There is a 500g weight that was used to increase friction because the molecules are being squeezed closer together. The rubber bands have a spring constant of 31.61 J and the spring potential energy is 175.26 J. The car, in general, is very efficient and works almost every time.
Major Physics Ideas Used in the Project
Distance v Time - A type of motion graph with time being the x-axis and distance being the y-axis. An object constantly moving forward will be graphed as a straight line on a distance vs time graph.
Example - Our vehicle was represented with a distance vs time graph. Since the vehicle was moving forward, the line was always going up. However, the line isn't straight because the vehicle's velocity changes over the time it travels.
Velocity (v) - The rate at which an object changes position. This is calculated by dividing the distance traveled by the time it took to travel. The unit is meters per second (m/s).
Example - We calculated the velocity of the vehicle at each meter. It had an average velocity of 2.42 m/s and a peak velocity of 3.3 m/s.
Spring Potential Energy (PE) - The amount of energy a stretched spring has. This is calculated by the equation 1/2kx^2. In other words, half the spring constant multiplied to the distance stretched squared. The unit is joules (J).
Example - The rubber band, when fully stretched 5 meters, had a spring potential energy of 175.26 J.
Gravitational Potential Energy (PE) - The amount of energy an object has at rest. This is calculated by multiplying the mass of the object, the acceleration due to gravity (9.8 m/s^2), and the height the object is raised. The unit is joules (J).
Example - Gravitational potential energy wasn't necessarily an important number in our vehicle because it was on the ground. However, if the vehicle were to use a ramp to gain its velocity, then it would have gravitational potential energy because it starts above the ground.
Kinetic Energy (KE) - This is energy due to motion of an object. This is calculated by the equation 1/2mv^2. This is half the mass multiplied to the velocity of the object squared. The unit is joules (J).
Example - The vehicle, when moving, had a peak kinetic energy of 7.0785 J. This is because the vehicle also had its peak velocity at the same time. Higher velocity means higher kinetic energy.
Thermal Energy (TE) - This is the amount of energy lost to heat or friction. This is calculated by subtracting the potential and kinetic energy from the total energy. The unit is joules (J).
Example - When the vehicle came to a stop, all the energy was lost as thermal energy (heat). On average, about 66% of the energy would be lost and converted to thermal energy each meter.
Total Energy - The total amount of energy in a closed system. This amount always stays the same, and is usually the starting potential energy. The unit is joules (J).
Example - The spring had a spring potential energy of 175.26 J. This means the total energy is also 175.26 J.
Friction - The force acting against the motion of the object. This is due to the roughness at the molecular level. The unit is newtons (N).
Example - Friction helped the vehicle stop. We used a 500g weight to increase the friction because it would originally slide past 5m.
Spring Constant (k) - Also called Hooke's Law, this is the tendency for a spring to return to its original state. This is calculated by dividing force applied onto the spring by the distance it stretched. Spring constant is a ratio, and is always constant with its rubber band. The unit is newtons over meters (N/m).
Example - The colossal rubber band we had had a spring constant 31.61 N/m.
Power (P) - This is the rate at which work is done. This is calculated by diving work by the time its distributed. But, this can also be used with kinetic energy by dividing kinetic energy by the time its distributed. The unit is watts (W).
Example - Our vehicle had an average power level of 11.467 W.
Example - Our vehicle was represented with a distance vs time graph. Since the vehicle was moving forward, the line was always going up. However, the line isn't straight because the vehicle's velocity changes over the time it travels.
Velocity (v) - The rate at which an object changes position. This is calculated by dividing the distance traveled by the time it took to travel. The unit is meters per second (m/s).
Example - We calculated the velocity of the vehicle at each meter. It had an average velocity of 2.42 m/s and a peak velocity of 3.3 m/s.
Spring Potential Energy (PE) - The amount of energy a stretched spring has. This is calculated by the equation 1/2kx^2. In other words, half the spring constant multiplied to the distance stretched squared. The unit is joules (J).
Example - The rubber band, when fully stretched 5 meters, had a spring potential energy of 175.26 J.
Gravitational Potential Energy (PE) - The amount of energy an object has at rest. This is calculated by multiplying the mass of the object, the acceleration due to gravity (9.8 m/s^2), and the height the object is raised. The unit is joules (J).
Example - Gravitational potential energy wasn't necessarily an important number in our vehicle because it was on the ground. However, if the vehicle were to use a ramp to gain its velocity, then it would have gravitational potential energy because it starts above the ground.
Kinetic Energy (KE) - This is energy due to motion of an object. This is calculated by the equation 1/2mv^2. This is half the mass multiplied to the velocity of the object squared. The unit is joules (J).
Example - The vehicle, when moving, had a peak kinetic energy of 7.0785 J. This is because the vehicle also had its peak velocity at the same time. Higher velocity means higher kinetic energy.
Thermal Energy (TE) - This is the amount of energy lost to heat or friction. This is calculated by subtracting the potential and kinetic energy from the total energy. The unit is joules (J).
Example - When the vehicle came to a stop, all the energy was lost as thermal energy (heat). On average, about 66% of the energy would be lost and converted to thermal energy each meter.
Total Energy - The total amount of energy in a closed system. This amount always stays the same, and is usually the starting potential energy. The unit is joules (J).
Example - The spring had a spring potential energy of 175.26 J. This means the total energy is also 175.26 J.
Friction - The force acting against the motion of the object. This is due to the roughness at the molecular level. The unit is newtons (N).
Example - Friction helped the vehicle stop. We used a 500g weight to increase the friction because it would originally slide past 5m.
Spring Constant (k) - Also called Hooke's Law, this is the tendency for a spring to return to its original state. This is calculated by dividing force applied onto the spring by the distance it stretched. Spring constant is a ratio, and is always constant with its rubber band. The unit is newtons over meters (N/m).
Example - The colossal rubber band we had had a spring constant 31.61 N/m.
Power (P) - This is the rate at which work is done. This is calculated by diving work by the time its distributed. But, this can also be used with kinetic energy by dividing kinetic energy by the time its distributed. The unit is watts (W).
Example - Our vehicle had an average power level of 11.467 W.
Reflection
I feel that my skills have improved from the trebuchet project. I fixed some of the original problems I had in the trebuchet project and made a better contribution to this project. My strengths were helping build the vehicle and figuring out the energies. In this project, I got a lot more hands on in the project. I focused on gluing the wood and helping drill in a hinge on the base. I was able to be a lot more active in the project, and I'm proud for that. I worked a lot on the energy graph. I calculated the potential and kinetic energies at each meter, the rate at which energy is lost, and the average kinetic energy. These numbers would play a significant role in creating the energy graph of the vehicle.
Unfortunately, for every problem fixed, there may be another one created. Some of my weaknesses were the friction explanation and the spring constant. During the creation of our presentation, I created the friction slide. However, I forgot to put in and explain a major component of the friction in which heavier objects have higher friction due to sliding closer to the ground. My group was deducted points due to this mistake. When we were calculating the spring constant, I used the entire 1.67 m rubber band rather than just one. As it turns out, using a 1.67 m doesn't work for spring constant because of the degradation of the rubber band over time and the general distribution of force. Because there are so many rubber bands, the distance stretched may be less since the rubber bands vary in strength, changing a lot of factors.
Even though I had a few problems, I feel that my contributions have significantly improved since the Physics of Sports video. I hope to keep up these improvements in future projects.
Unfortunately, for every problem fixed, there may be another one created. Some of my weaknesses were the friction explanation and the spring constant. During the creation of our presentation, I created the friction slide. However, I forgot to put in and explain a major component of the friction in which heavier objects have higher friction due to sliding closer to the ground. My group was deducted points due to this mistake. When we were calculating the spring constant, I used the entire 1.67 m rubber band rather than just one. As it turns out, using a 1.67 m doesn't work for spring constant because of the degradation of the rubber band over time and the general distribution of force. Because there are so many rubber bands, the distance stretched may be less since the rubber bands vary in strength, changing a lot of factors.
Even though I had a few problems, I feel that my contributions have significantly improved since the Physics of Sports video. I hope to keep up these improvements in future projects.