Projectile Motion
Launching a Projectile
Our Goal
My class was tasked with building a device that would launch a projectile off of a table of any height between 0.7 meters and 2 meters tall accurately onto a set target. To do this my group needed to calculate exit velocity and the distance the object would travel at from our device using kinematics equations. Additionally we were encouraged to modify one variable three times in our beginning rounds of trials and use the modification that was most consistent for the final launch. We were then challenged to assemble the device in less than 3 minutes on launch day.
Our device consisted of a hotwheels car launcher, rubberbands, a toy car, and a flat orange ramp. The piece that our group modified was the number of rubber bands attached to the car launcher. We ran trials for 1, 2, and 3 rubber bands, found the exit velocity and landing location for each from our standard table (0.87 meters tall), and decided to use 2 for the final challenge. For the day of the launch, the new table height was 1.17 meters tall and we were successfully able to set a target at a predicted landing location with 95% accuracy.
The kinematics equations we used to derive equations for time and exit velocity were:
y = y0 + vy0t + ½ at2
v = change of x/change of t
vx = △x/√(2△y/ag)
Below is my lab report from the project with the specifics of our findings with more detailed explanations.
Content
Velocity - The rate at which something moves in a certain direction. Velocity is calculated by dividing distance by time. The unit is meters over seconds. v = d/t. We used this equation to find the vertical velocity of our projectile in this project.
Free fall - An object is in freefall when gravity is the only force acting upon it. The acceleration is constant (-9.8m/s²). Once our projectile was released from our device, it was in free fall.
Newton's Second Law - States that the sum of all forces on an object equals the mass multiplied by the acceleration. F=ma
Friction - Friction is a force that opposes motion. Friction is equal to the normal force multiplied by the coefficient of friction. This semester we learned about three types of friction: static, sliding, and rolling.
Normal Force - Normal force is the force of the surface an object is resting on back on that object to prevent it from falling through the surface. This force is perpendicular to the angle of the surface. It is equal in magnitude and opposite in direction to the vertical force of gravity.
Block and Tackle - Also known as pulleys and masses, they are an arrangement of rope and pulleys that allow a system to trade force for distance to lift heavy weights.
Gravity and Orbits - Gravity is a force that attracts things with mass towards each other. An orbit occurs due to gravity, and is a repeating path which a celestial object takes around an object with greater force of gravity. Gravitational force equation: F = G(m1m2)/R2
Acceleration - The rate of change of velocity. Acceleration is calculated by dividing the change of velocity by the change of time. The unit is meters over seconds squared. a = v/t.
Force - A force is an influence that can change the motion of an object with mass. A force can be found using Newton's 2nd Law: F=ma.
Newton's First Law - This law of inertia states that an object at rest remains at rest and an object in motion remains at motion unless an outside force acts upon it.
Newton's Third Law - States that for every force there is an equal and opposite force. Every action has an equal and opposite reaction.
Air Resistance - Also known as drag, it is a force acting opposite to the relative motion of any object moving. Drag is found using the equation: D=1/4 p A v^2.
Tension - Tension is a force transmitted through a string of some kind. This force is consistent through the whole line.
Circular Motion - A movement of an object along the circumference of a circle or rotation along a circular path.
Period - The time it takes for one complete cycle. It it represented by T.
Energy - Characterized by the ability to do work. It can neither be created nor destroyed, but it can be transformed between forms. A few forms we have learned about are thermal, kinetic, and potential energy. They are each found using different equations.
Reflection
Over this first semester of AP Physics, I did well at building a habit of doing the work each week to make sure I understood the material. This course has been challenging for me so far, and so for many of the units I had to put in extra time outside of completing the homework to fully grasp the concepts that did not make sense right away, utilizing my older sister as a key resource. I think this shows my perseverance as a conscientious learner, and my ability to prioritize my time in order to succeed. I also was able to build on my skill of communication because I often needed to ask for help and clarification.
Some aspects I am still working on and can look forward to improving in the next semester are taking more time in the planning stages of projects and improving my attitude towards the work. In a few of the projects this year, my groups have been quick to start the project without fully thinking it through. For instance, in this lab, we used rubber bands to launch the car, without realizing that rubber bands stretch out and vary from day to day until it was too late. In the future, I will try to run through the execution of the project in my head to make sure we're being proficient and not complicating things for ourselves. In addition, this period at the end of the semester I often found myself dragging through the work and procrastinating, when the work was not any harder than it had been all semester. Next semester, I will try and keep a more positive outlook on school in general and not build it up to be worse than it actually is.