LAB #8 - Lab report PDF

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1-a)Introduction Law of conservation of energy states that the total energy of the system remains same, and energy cannot be created or diminish, it can just transform from one form to another. Mechanical energy consists two types of energy, Potential energy (energy that is stored) and kinetic energy (energy of motion). When an object falls from a specific height, it transform from potential to kinetic energy.

b) Objective The objective is to explore the concept of mechanical energy, and also to understand energy transfer and the law of conservation of energy. By performing the experiment and learn how the energy is conserved, and how this law was made by someone.

2- Theory a) Theoretical background In physics, the law of Conservation of Energy states that the total energy of an isolated system remains constant, it is said to be conserved over time. This law means that energy can neither be created nor destroyed; rather, it can only be transformed from one form to another. In 1842, Julius Robert Mayer discovered the Law of Conservation of Energy. Mechanical energy is the sum of the potential and kinetic energies in a system. The principle of the conservation of mechanical energy states that the total mechanical energy in a system (i.e., the sum of the potential plus kinetic energies) remains constant as long as the only forces acting are conservative forces.

b) Equations 1 m v 2 , PE= mgh KE= 2 1 (M +m) v2 , Loss in PE= mgh Increase in KE= 2 d Velocity of car, v= t PE❑loss =KE❑gain P E loss−K E gain × 100 % difference= averageof P Eloss ∧K E gain c) Diagrams

3- Experiment a) List of Equipment ●

Air track, Gliders, Masses, Stopwatch, Beam Balance, 2 photogates.

b) Experimental Diagram

c) Procedure Level the air track, and measure the mass of the car and the distance between the photo gates. While place car, make sure the air is off so that the masses hand about a meter above the ground. Make sure the strings runs through the pulleys correctly, also make sure that when the masses hit the ground, the car has not yet reached the first photo sensor. Turn on the air to start the masses falling and the car moving. Record time, and repeat several times with different amount of masses.

4- Results a) Data tables m=mass on hanger + mass of hanger (g)

Convert m to kg (kg)

Height H (m)

Time t (s)

Velocity V (m/s)

Loss of potential energy (J)

Increase in Kinetic energy (J)

Average of Ploss and Kgain

% difference between Ploss and K gain

5

0.005

1

0.35

0.57

0.049

0.048

0.0485

2

10

0.010

1

0.26

0.77

0.098

0.089

0.094

9

15

0.015

1

0.22

0.90

0.147

0.125

0.136

16

20

0.020

1

0.19

1.1

0.196

0.191

0.194

3

25

0.025

1

0.17

1.2

0.245

0.230

0.238

6

30

0.030

1

0.16

1.3

0.294

0.275

0.284

7

35

0.035

1

0.15

1.3

0.343

0.279

0.311

20

40

0.040

1

0.14

1.4

0.392

0.329

0.361

17

Mass of car, M = 295.3 g ; 0.2953 kg , distance between sensors d = 20 cm ; 0.2 m.

b) Graph

No Graph

c) Error Calculations, Accuracy Accuracy depends on the friction of the surface, because friction transform energy to other forms, like heat/thermal, and sound energy. So the more the friction, the more the difference will be in the results. Also it depends on the air track, sometimes it is not level. And sometimes the string goes off from the pulley which also cause problems in the experiment.

5- Discussion of Results a) Possible sources of error The possible errors in the lab may have come from the inaccuracy of placing the photogate. Also when assembling the glider. Sometimes our group would touch the photogate which is not good for the experiment. Also rounding the results did not give us precise data. Also an average time should be calculated for each trial to get an accurate time. Our group had tried one trial on the glider twice and different times were given in some of the cases.

b) Observations Through this lab, I observed that energy is never created or destroyed, but changing forms. I learned that the mechanical energy of potential and kinetic energy are constant and equals. As one goes down the other goes up. (Reversible). We apply this conservation of energy to everything we do. All our actions have stored potential energy, once we move, that potential energy is converted into kinetic energy. For example when we are weighing the glider more the energy was more because of the gravitational forces. At the height, we are not moving, but we have stored potential energy. When we turn on the air that potential energy is converted to kinetic energy as we speed up, and the masses touch the ground.

c) Suggestions I will suggest to not touch photogates, and check the string after every trial, and make sure it goes through the pulleys. Also I suggest that round the time you get in every trial, so it can be as close as possible or same. If it is same that will be really good. I also suggest to do every trial twice, and then record the average time, it must be almost same, if there is no human error has been occur.

6- Conclusion Q1-Our purpose was to test the law of conservation of energy and the mechanical. It is a law so it must be correct as we found in the experiment. We might see differences in our energy, and some of the people might be thinking the energy is gone, but that is not true. Because of friction energy has changed the form. Energy cannot be created or destroyed.

Q2- Velocity and time both has trend in this experiment as asked in the question. While we increase mass time decreases, and velocity increases after each trial. The trend is expected because if there is more mass the speed of the glider will increase, because the more mass is pulling the glider.

Q3- In this case Ploss is more than the Kgain, it should be same but because of friction there is some difference. There is more Friction in Kgain than the Ploss , so the more energy is transferring to thermal and sound in Kgain, as compare to Ploss, That is Ploss is more than Kgain.

Q4- There was air resistance and friction that was not accounted for. Minor errors like these could have resulted in different data results than what should have happened in a perfect environment. In the experiment, preparation for avoiding these errors was taken into account and hopefully these mishaps did not occur. The results of the data showed that the theory that total energy was constant proved to be true, with some exception to experimental error. When the object started from the same origin, the potential and kinetic energies totaled about the same amount on each trial, no matter where the photogate was. As the potential energy increased, the kinetic energy decreased, and when the potential energy decreased, the kinetic energy increased. The equipment we used will also not give us the accurate results as there are many other equipment which could have been used to get more precise and accurate results. Specially the environment is the most probable thing to note here, because daily life environment will never give the best results....