Projectiles Force

To calculate the force acting on the trebuchet, one must know the initial velocity which launches the ball and the angle at which the ball is launched. Also, the law of conservation of energy (kinetic and potential) is involved in this calculation.

Projectiles - Write Up

http://www.youtube.com/watch?v=7xO-TCB0t70

1.       What was your original construction idea?

Our original idea is doing a small trebuchet that have enough force to launch the tennis ball. This trebuchet requires human power to launch. 

2.       What challenges did you face in construction?

Measuring the material and assembling those parts are quite exhausting as we have to make sure that everything is fit together . Our final trebuchet is bigger than our original idea, so it requires more effort. 

3.       Did you stick with your original plan?  Why or why not?

We didn't stick to original plan. We thought about how small that was, so we determined to do the big trebuchet that launched the ball further.

4.       Explain how your device works.

We attach the counterweight to the short arm. It is about 40 lbs. We also use the string as device to launch the projectile. The ball will be placed in the basket resting on the base. When we pull the string, it will release the long arm. The counterweight will fall down, launching the ball as the long arm goes up.

5.       Where and how was this device used in history?

It was used extensively in the Middle Ages by the French. Medieval Trebuchets could launch missiles hundreds of yards at, or even over, a castle, fortress or city wall.

6.       What did you learn by constructing this device?

We learn how to construct and build a device that applying physics' theory. 

7.       What principals of physics did you utilize in this device?

We use the law of gravitational potential energy to build the trebuchet. We also apply  Conservation of Energy law. 

8.       Tell about a career where this type of device could be useful.
These trebuchet can be used in the military. Those office in military might use trebuchet to throw dead bodies or destroy castles ( which I don't usually see). Physics teacher or students major in Physics can learn how to build trebuchet to understand more about the law of physics.

9.       Could this type of device be useful in getting people to space?  Why or why not?

The escape velocity is approximately 25,053 mph. This velocity is required for the device to escape the earth and go to space. It is nearly impossible to use trebuchet for this purpose. 

Projectiles - Test Fires

We didn't do well on the accuracy test. The angle of the releasing pin on the swing arm was not consistent. We must change the angle of the pin each time of the test. The accuracy distance, therefore, was affected by the pin.

Projectiles - Safety Concerns

Safety is the most important thing to be considered when building the trebuchet. Any loose parts must be tightened. The trebuchet must be stable when firing or it will cause danger. The weight attached to the short level arms must be firm. When firing, no one should be standing near the front and the end of the projectile. Everybody should be away 2m from the projectiles and wearing goggles.

Rube Goldberg - Final Submission

Here is our final lab: https://www.youtube.com/watch?v=_w5GLvRXEwE

 Most energy is lost as Eliza letting the marble slide down. As the marble slides down, its potential energy is being converted into kinetic energy. The total energy is always conserved. I will pick the first energy change, which is potential energy to kinetic energy, to perform my calculation. In order to know how much energy changes during this section, first I need to know at what height the marble is rolling down. Height and the mass of the marble are also taken into consideration. For this, I will determine the final energy at the end of the first energy change. The change in kinetic energy indicates the work of the marble. Its power can be calculated using its force and velocity; the product of these two components will give me the power of the marble. Total energy is very much simple since it is either the initial potential energy or the final kinetic energy.

This lab is a good experience for me as I learn a lot through it. Working with other students sometimes pisses me off, but as we comes together and agree on our ideas it is pretty easy to overcome the task. This assignment gives me a good knowledge of what I would be doing in college. I hope we can have few more of this the rest of the year.

Rube Goldberg - Lab Report

At first when we were drafting the sketch, we gathered ideas from each of us and put them together. Our first idea was devising a system that makes a coffee as a final task. That idea, however, could not be accomplished due to changes in our materials and unexpected problems during making devices. When we started to set up devices and tried to connect them together, we realized that it was really different from what we had drawn on the paper. Thus, we started going step by step by setting up the first device and then thinking about the next device that was able to connect to it. Because we did not have many spaces, we had to take advantage of any space that we could on two tables. I remembered that we could not find any chemical energy transfer, so in the end we must change our final task, which is chemical energy transfer, to make it connected to the rest of the system. Through this lab, we were able to learn that we must anticipate unexpected problems and find the way to fix them.

Rube Goldberg - Post 1

When we started to build this device, we faced the tough challenge in connecting those separated devices together. Because we started drafting the sketch without knowing unexpected problems lie in the device, we failed every time we tried to connect it together. After every failure, we went back and fixed that particular place where it did not connect to the rest of the device. I can say that the toughest problem in this lab is how to connect each energy transfer together, each following the previous one.

Work and Power Lab

5.1.1: Measuring Work:

1. Because work involves the force over a distance, so the force, which is the weight of a person, depends on a person's mass. Also, work is directly proportional to force; therefore, a person weight twice as much as his friend will do twice the work.
2. If you travel along the distance from the bottom step to the top step, you are doing no work on it because you are not moving it against the force of gravity.
3. Work is the change of kinetic energy, whereas impulse is the change of momentum.
4. The work of lifting a 2000-N object a vertical distance of 10m would be equal the work of lifting a 1000-N object a vertical distance of 20m.
6. The work does not depend on time because work is defined as the product of force over a distance, which do not involve time.
7. In half revolution, the wheel travel a distance of half the circumference (pi). Work is 31.41 J.
In a complete revolution, the wheel travel a distance of 2pi(r). Work is 62.83 J.

5.1.2: Measuring Power:

1. As a person runs up the ramp in half the time of another person of equal weight, he does the same work but uses twice the power because work does not involve time while power is the work over a time period. Half of the time will cause the power to double because they have inversely proportional relationship.
2. As the vertical height of the stair is reduced by half, the work will be half of its original work. Thus, power will be reduced by half. (work and power are directly proportional).
3. It is not necessary to use greater power to perform such fears because the power indicates the work over a time period.
4. 1 hp = 745.7 Watts. The work done is (745.7W)(60s) = 44742 J. Gallons of water: 1182 gallons.
5. Power in horsepower of a 100-watt light bulb: 0.134 HP
Power in kilowatts of a 200-horsepower engine: 149.14 kW.

5.1.3: Reading Your Electric Meter:

1. 5003kWh - 3866kWh = 1137 kWh
2.

3. Because we keep consuming energy, graph of household energy consumption varies from day to day.

4. 5793kWh - 5459kWh = 334kWh. It costs $24.34.

5.1.4: Conserving Electricity

1. Unit of electric energy is kWh, while unit of electric power is W

2. I will use more energy than my friend ( 50kWh > 40kWh)

3. Power accounts for the great difference in consumption energy.

4. 1450 MW = 1450 x 10^6 W = 1450000 kW

Hooke's Law Lab

Spring

Rubber Band

1. There must be error in data because of human error like measuring the length inaccurately. Or it could be that we measured the length of the spring when it was still vibrating.
3. If you overstretch a spring or rubber band, it will cause the spring/rubber band to lose its elasticity constant. Therefore, it will affect the final result.
4. The graph force vs stretched length will give a straight line. Its slope indicates the spring constant of the spring.
5. Based on my result, the rubber band does not obey Hooke's Law because its spring constant varies too much.
6. The spring constant of the rubber band depends on the nature, the length, and the thickness of the rubber band. These will cause a difference in its spring constant.

Soda Bottle - Post Lab

• How much force is necessary to dislodge the stopper from the bottle?

The force that the stopper exerts on the bottle and the force the bottle exerts on the stopper do not cancel out. These forces act on the different object, despite that they have equal magnitude. So the force is necessary to dislodge the stopper from the bottle depends on the mass of the stopper, and perhaps mass of the bottle.


Question:

1. If one object pushes a force on another object, it will be pushed back with an equal but opposite magnitude.
2. As the gun is fired, it applies a force to launch the bullet. The bullet will push a force back to the gun, causing the gun recoils
3. The force that a ball applies to the paddle as well as the paddle applies to a ball is constant. The paddle has larger mass than the ball, so the paddle will accelerates slower than the ball. It will be hard to observe the motion of the paddle as being pushed back.

Real-world situations:

1. In launching the rocket to the space, people at NASA apply Newton's Third Law. At lift-off, hot burning gas is pushed downwards by the rocket motors. The hot gas pushes back on the rocket in an upwards direction. When this upwards push exceeds the weight of the rocket, the forces acting on the rocket are unbalanced and the rocket accelerates upwards.
2. As you are driving your car on the road. The car has to exert a force against the road. And the road has to exert the same force on your car. Otherwise, the car wouldn't be accelerating.
3. The hunter shoots the bullet from a gun. As the bullet flying out of the gun, it causes a recoil in the gun, exerting a force that pushes back the hunter. That is why he feels his body being pushed backwards. 

Soda Bottle - The Lab

Observation: As we pour the baking soda into the aluminum foil and put it inside the bottle, the bottle is filled with vinegar already. When we shake or rotate the bottle, baking soda will react with vinegar to create carbon dioxide. Carbon dioxide is created; thus, increases the pressure inside the bottle. When the bottle cannot hold enough pressure, the stopper will fly out and applies an opposite force to the bottle, causing the bottle accelerates backward.

Data:

Error analysis: Human error could be one thing to be considered. There might be errors in data as we measure the baking soda, and the vinegar. The mass of the bottle is also important because it determines the force that applying on the stopper and the bottle itself. More vinegar and baking should be used in the bigger bottle.

Coefficient of Friction Lab

Procedure: Choose 1 material and 1 surface from the given list. Measure the mass of the material. Attach Newton's scale to the material and drag it along on the surface. Record the force it takes to move along the surface. Calculate the coefficient of friction using the formula F(friction) = umg.

Data & Calculation:

Error Analysis: There should be error in this lab due to small mass of materials. Small mass will lead to small friction force, which is hard to determine. Also, there might be some error in recording the force.

P.S: I actually don't like what I did. I think the way I did the lab (especially the friction force) is totally wrong. In my opinion, the force that I had from the Newton's scale is actually the applied force. To figure out what the friction force is, I must know the velocity of the object. The friction force should be F(applied) - F(friction) = ma

Soda Bottle Pre-Lab

Hypothesis: The carbon dioxide rocket is performed based on the Newton's Third Law. As the vinegar and baking soda mix together when the bottle is rotated, the reaction takes place and carbon dioxide (CO2) is produced. Carbon dioxide will cause the cork flies forward. As the cork flies forward, it applies the equal force but opposite direction to the container, making the container flies in the opposite way.

Procedure: Pour 200 mL of fresh vinegar into a 2-liter plastic container. Place a rubber stopper in the mouth of the container and then position it on round pencils. Then use aluminum foil to make a trough. Fill the trough with baking soda and carefully insert it into the mouth of the bottle. When everything is set up completely, rotate the bottle. The baking soda and vinegar will mix together and produce carbon dioxide, which makes the stopper flies out of the mouth and cause the container flies backward.

• How much force is necessary to dislodge the stopper from the bottle?

Measure the mass of the stopper and the bottle (with vinegar). Record the time that the stopper moving. Measure the distance the stopper travels after being dislodged from the bottle. Calculate the acceleration the stopper using the motion equations. Find the force acting on the stopper using Newton's Second Law.

Washer/Elevator Lab

Washer Lab:

• Observation: As we pull the washers at constant velocity, its weight is equivalent to its resting weight. When the washers, however, accelerates upward, its weight is greater than its resting weight. When the washers accelerates downward, its weight is smaller than its resting weight

Question: 1) When the scale was decelerating, the value of a is negative; whereas when the scale was accelerating, the value of a is positive.
2) The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma.

Example: The toy car has a mass of 2kg. The car is accelerating with the acceleration of 2m/s^2. The applied force on the toy car is F = ma = (2kg)(2m/s^2) = 4 N.

3) If the air friction is negligible, a feather and a rock will hit the ground at the same time because free fall does not depend on the mass of an object.

4) As the force is held constant, mass of an object decreases will cause the acceleration increases because mass and acceleration have an inversely proportional relationship.

Elevator Lab:

Procedure: Record person's actual weight. Then record his weight as the elevator accelerates upward or downward.

Data: Person's mass: 179 lbs ~ 81.19 kg

Mass when elevator accelerates upward: 182 lbs ~ 82.55 kg

Mass when elevator accelerates downward: 176 lbs ~ 79.83 kg

Calculation: 

Upward: mg + ma = 82.55kg 

=> 81.19 ( -9.8 ms-2 + a) = 82.55

=> a = 10.82 ms-2

Downward: mg + ma = 79.83 kg

=> 81.19 ( 9.8 ms-s + a) = 79.83

=> a = -8.82 ms-2

Error Analysis: There will be slight errors in recording the person's weight.

Ballistic Pendulum 3

Post lab questions:

Initiative:

In my opinion, the kinematics experiment provides a more accurate data than the pendulum does. One possibility involves the distance being measured. In the kinematics experiment, a projectile is launched several meters from its source. The point of impact is then measured from the launch point. The pendulum experiment however involves measuring the difference in height of the center of mass of a pendulum. The heights measured are really small, and are only a fraction of that length. One additional possibility is in the pendulum experiments, as we tried 5 times, the ball always bounced off and did not completely attached to the pendulum bob. This will cause the error in the total mass after the collision, thus, lead to an error in the final velocity. 

Ballistic Pendulum 2

Observation: 

• Experiment 1: As the ball is fired from the gun, it will hit the pendulum bob and causes the pendulum bob rise a height h. By measuring the height h the pendulum bob rises, I can calculate the initial velocity of the ball before the collision.

• Experiment 2: As the ball is fired from the gun at height h on the table, it will travel in a projectile motion and land on a carbon paper placed on the floor. By measuring the distance that the ball travels horizontally, I can figure out the horizontal velocity of the ball.

Data: 

 Error Analysis:
The percent difference from 2 experiment is 15%. There must be, however, a possibility of human error. Perhaps we marked the wrong spot on a carbon paper during the experiment 2(lead to the wrong data in the distance the ball travels horizontally), or measured the angle inaccurately in experiment 1(lead to the wrong data in height). In addition, there will be a difference in initial velocity of these experiments because the launcher, in fact, did not launch the ball at the same velocity each time.

Ballistic Pendulum Lab 1

Procedure: 
    Part 1: Momentum and Kinetic Energy after the collision

• Measuring the masses of two bodies.
• Measuring the distance from the tabletop to the center of mass of the pendulum before collision (h1) and after collision (h2)
• Fire the steel ball (mass m) into the hollow pendulum.
• After the collision the pendulum will be brought to rest at its highest point by a set of ratchet teeth mounted on the base of instrument. Then, measure the distance, h, that the pendulum was raised (h = h2 - h1). Repeat this step 5 times and record all data. 
• Add the masses of the two bodies, then calculate the initial velocity of the projectile using the conservation of energy and conservation of momentum equations.

    Part 2: Momentum and Kinetic Energy before the collision

• Measuring the distance from the launch point to the edge of the paper (x1) and from the edge of the paper to the center of the shot distribution. (d)
• Fire the projectile across the room.
• Place a piece of carbon paper (carbon side up) on the landing spot and tape a white sheet of paper on top of the carbon.
• The ball will leave a mark when it lands. Determine the range of the projectile by measuring the location of the marks (x = x1 + d). Repeat 5 times and record all data.

Hypothesis: As after the collision, the pendulum will raise to h height. Kinetic energy will transform to potential energy. Total energy is always conserved. The momentum also is conserved.

Materials: The pendulum, launcher, carbon paper, measuring tape

Velocity and Acceleration Lab 2

Although there is a slightly different change in time, two Buggies are likely to travel with constant velocity. Blue Buggies takes little more time to reach the end. There were some unexpected errors during the: they slightly changed their direction while traveling, thus, causing a really really small acceleration. However, if the lab was performed perfectly, there would be no acceleration.
The velocity for Red Buggies is .51m/s; the velocity for Blue Buggies is .45m/s

Velocity and Acceleration Lab

Procedures: Mark every 1 meter on the floor with the measuring tape. Let 2 Dune Buggies (Red and Blue) run 7 meter total at the same time. Each time Buggies reach 1 meter, record the time. When have all of data, calculate the velocity the buggies travel during 1 meter, repeat the calculation 7 times for each buggy. Then, compare those values.

Observation: Based on the data from the lab, I think two Buggies travel with constant velocity.

 Data Table:

Vector Lab 2

When I was measuring the distance, I did it in feet. So I had to convert it to meter to meet the criteria. There must be some small error in data because I measured the long distance few times before adding them up. I think the hardest part is calculate the angle and direction of the displacement vector. Since the vector is in 3D, it is confusing to figure out the angle on the 3D graph.

1st and 2nd period:

3rd and 4th period:

5th period:

6th and 7th period:

Vector Lab

When I started this lab, I hadn't considered about 3-dimensional vector. I was surprised; it took me few minutes to choose the origin and determined the x,y,z axis. My initial thought was measuring x and y component, and then figure out displacement for each class. The material that I used to perform this lab was only a measuring tape. It was inconvenient to measure the long hallway with these measuring tape. 

Here is the data table.

Physics AP!!!

I love to learn about how things around me working. When I was young, I read an articles about Einstein and Newton; I admired them so much. I took Chemistry AP last year. I learnt so many things that was very helpful to me. In college, I am going to major in Mechanical Engineering and I know it requires lots of Physics knowledges. So I want to took this class to prepare for my education in college. I believe this class will help me successful in college and trigger my passion in Physics.