10-Oct-2016: Magnetic Potential Energy

Lab 13: Magnetic Potential Energy
Name: Andrew Martinez
Lab Partner: Richard Mendoza

Statement: To verify that conservation of energy applies to this lab

Introduction: To find an equation for magnetic potential energy. To find the magnetic potential energy for a non-constant potential energy one must recognize the relationship between potential energy and force. The relationship appears as U(r)= - (integral ^r _infinity) F(r)dr.

Apparatus: Air track (Friction less surface), glider, magnets, air pump, books

Books were used to raise the air track to multiple angles to plot the separation distance

Procedure
- Level the air track to measure the variable h.
- From h this will be the position the experiment is done at.
- Collect data from various angles to plot a relationship between magnetic force F and the separation distance r.
- Plot F vs r graph. The relationship in this graph is a power law F = Ar^n. Find A and n from the curve fit performed on the graph
- Verify conservation of energy
- Attach an aluminum reflector
- Weigh the cart
- Determine the relationship between the distance the motion detector reads and the separation distance between the magnets
- Make a single graph showing KE, PE, and total energy of the system as a function of time.

Measured Data:
Using books we take the angle of the air track at different points and measuring the separation distance between the glider and the magnet. (+/- .1 degrees, +/- .2 mm).
1. .6 degrees, 22.2 mm
2. 2.1 degrees, 18.2 mm
3. 4.0 degrees, 14.1 mm
4. 5.2 degrees, 12.9 mm
5. 8.3 degrees, 10.6 mm
Convert mm to meters

Using this data we can use the equation F_mag=sin(theta)mg to find the force of the magnet
1. .03456 N
2. .210554 N
3. .2304 N
4. .299 N
5. .477 N

Graphed Data:
Using the measure data we plot a Distance(r)(x-axis) vs. Forces(F)(y-axis)

Using graph we perform a curve fit to find the A=2.363*10^-6 (+/- 1.368*10^-6) and n=-2.690 (+/- 0.1301) to plug into a power law (F=Ar^n)

Using the graphs we can verify that conservation of energy applies to this system

The bottom graph represents the single graph of KE, PE, and total energy as a function of time. As can be seen the graphs come together at a single point.

Conclusion: Despite knowing that conservation of momentum does apply to this experiment based on our graphs results it can not be proven with the data provided. Their are a number of reasons why the graphs fails to show the conservation of energy but one must likely answer is due to systematic error where the human element may have miscalculated or used a wrong equation. 

14-Oct-2016: Work-Kinetic Energy Theorem Lab

Lab 11: Work-Kinetic Energy Theorem
Name: Andrew Martinez,
Lab Partner: Richard Mendoza, Lynel Ornedo, Mohammed Karim

Statement: In experiment 1 the object is to calculate work done by finding the area under the graph. In experiment 2 the objective is to find the spring constant.

Introduction: This lab is divided into two parts called EXPT 1: Work Done by a Non-constant Spring Force and EXPT 2: Kinetic Energy and the Work-Kinetic Energy Principle. The main objective of EXPT 1 is to find the work done by force by using the area and EXPT 2 is to find the spring constant by using graphs.

Apparatus

Cart attached to a spring and placed upon a long horizontal surface. A force probe is placed on the other end of the track to record the force over the distance traveled.

EXPT 1: Work Done by a Nonconstant Spring Force

Procedure
- Calibrate the force probe with a force of 4.9 applied
- Set up the apparatus
- Ensure that the motion detector is able to detect the cart.
-  Open up the file L11E2-2 and zero the force probe. Then begin graphing the force vs position graph as the cart is pushed forced to about .6 m
- Determine the spring constant and explain how
- Use integration routine in the software to find work done by the stretch of the spring.

Data recorded by the software as the cart is slowly pushed towards the force probe. The force probe should be set to reverse direction to plot in the positive x direction. We then use a linear fit to find the spring constant which should be our slope. Slope is 8.828 N/m which is the spring constant. We know that this is true because of hooke's law that states a spring force is equal to the spring constant times its position or F=k*x.

When then use the integration routine to find the work done by stretching the spring which is shown to be .3930 Nm W=F*d or work equals force times displacement but in this case we are using the area under the graph to find the work done by the spring. 

EXPT 2: Kinetic Energy and The Work-Kinetic Energy Principle

Procedure
- Measure the mass of the cart m=.6997 kg
- In new calculated column use a formula to find kinetic energy of the cart at any given point
- Repeat steps in previous experiment for setup
-  Find the change in kinetic energy after the cart is released from the initial to several different positions
- Find the work done by the spring up to those differing positions

Graph Analysis

As shown by the graphs we can find the work done at different positions as well as the kinetic energy

Conclusion: The work done on the cart by the spring shows how kinetic energy changes in relation to work. Since we know that F=k*x and that W=F*d we can see how the change in the kinetic energy of an object is equal to the net work done on the object and thus proves the work-kinetic energy principle.

3-Oct-2016: Centripetal Force with a Motor

Lab 9 Centripetal Force with a Motor
Date: 03 October 2016
Name: Andrew Martinez
Lab Partners: Richard Mendoza, Lynel Ornedo, Mohammed Karim

Statement: To determine the relationship between theta and omega.

Introduction: As angular speed increase due to the motor spin the mass shifts to a larger radius resulting in an increase in angle theta.

Apparatus:

An electric motor mounted on a surveying tripod. Long string tied to the end of the horizontal rod. Rubber stopper at the end of the string.

Long shaft going vertically up from shaft with a horizontal rod mounted on the vertical rod. Ring stand with a horizontal piece of paper on tape sticking out.

Procedure
- The professor has control over the motor and thus can increase it for the experiment.
- The students use the vertical stand that with the paper sticking out to find the mass height from the ground.
- Students are also responsible for measuring the amount of time it takes for the mass to make ten rotations
- Using all the measured data students can then conceptually break down the components of the centripetal force to derive an equation for omega
- Using your actual and calculated values one can then graph these omegas to how close the correlation is and the percent error to see if theta is related to omega.

Measured Data

Using our understanding of centripetal forces we are able to derive equations and variables based upon this understanding. Through this we can display the relationship between θ and ω.

On this page we derive several equations to help in proving the relationship between theta and omega. H is a constant as it stands for the vertical stands height. Little h is the shifting height of the swinging mass as the motor increases in speed. L is the length of the string and while the swinging mass may shift height L will always maintain its length. Knowing this we can find theta through SOH CAH TOA. Since only A(H-h) and H(L) are known we can use the arccosine to find theta. Since we know that omega is equal to theta divided by time we can find the actual omega.

In this picture we are trying to derive an equation to find omega by calculation and understanding of centripetal force. We break our net centripetal force into its X and Y components where Fx: Tsinθ=mrω^2, Fy: Tcosθ-mg=0. By setting T=mg/cosθ we can substitute into T to solve for omega as seen above where the masses cancel each other out, sin over cos can be changed into tan and r is r+Lsinθ to account for the changing radius.

 Graphing Analysis

By graphing our actual values of omega and the calculated value of omega and performing a linear fit with a correlation we can see that the correlation is .9999 almost at 1. 

Upon conducting a percent error test we can see that the actual and calculated values are reasonable close to each other and that by doing so we can see that their is a relationship between omega and theta.

 Conclusion: Based on our results we can conclude that there is a relationship between omega and theta. For as theta increase so did omega and that by deriving an equation for omega through trigonometry and using theta we were able to get accurate results for omega.  Based upon our low percent errors it is safe to presume that theta is related to omega. One concern that should be noted in the rising percent error as the values went further along. Some possibilities for this could be a random error of changing speed in the motor or a systematic error of timing of the rotations.

28-Sept-2016: Centripetal Force Lab

Lab 8: Centripetal Force with changing mass, radius, and angular velocity
Name: Andrew Martinez
Lab Partner: Professor Phillip Wolf

Purpose: To determine the relationship between centripetal force and mass, centripetal force and radius, and centripetal force and angular velocity.

Theory/Introduction: To find centripetal force the formula F_centripetal = mrw^2 is used where w is the angular velocity, r is the radius, and m is the mass. By varying the values on m, r, and w separately and then graphing in a centripetal force vs (varying variable) our slope will equal our constant values and prove their relationship to one another and to the formula.

Apparatus: Was a custom made motor that spun in a circular motion. A time gate with some mass was fasted to the spinning panel and measured for the varying variables.

Measured Data

Trail 1: M=200 g, R= 19 cm, V=6.1 Volts, Delta Theta = 20pi, Delta T=.43s-20.63s, F=0.392 N
Trail 2: M=200 g, R= 28.5 cm, V= 6.1 V, Delta Theta= 20pi, Delta T=1.27s-19.28, F=0.837 N
Trail 3: M=200 g, R=40 cm, V=6.1 V, Delta Theta= 20pi, Delta T=.55s-16.7s, F=1.39 N
Trail 4: M=200 g, R=54 cm, V=6.1 V, Delta Theta= 20pi, Delta T=.94s-17.47s F=1.65 N
Trail 5: M=200 g, R=54 cm, V=6.6 V, Delta Theta=20pi, Delta T=.2s-13.1s F= 2.61 N
Trail 6: M=200 g, R=54 cm, V=7 V, Delta Theta= 20pi, Delta T=.7s-12.5s, F=3.37 N
Trail 7: M=200 g, R=54 cm, V=7.7 V Delta Theta=20pi, Delta T=.32s-10.04s, F=4.79 N
Trail 8: M=100 g, R=54 cm, V=7.7 V, Delta Theta=20pi, Delta T=.6s-10.4s, F=2.3 N
Trail 9: M=50 g, R=54 cm, V= 7.7 V, Delta Theta=20pi, Delta T=.31s-10.54s, F=1.14 N

Graphing Analysis

In this Force vs Rw^2 graph the variable m for mass is kept constant. By comparing the slope to the actual M one can see how accurate the equation F=mrw^2 is.  In this case the slope of mass is 0.21 when our actual mass is 0.2 which means we had a 5% percent error which is an acceptable margin of error.

In this Force vs w^2 graph the variable mr for mass and radius is kept constant. By comparing the slope to the actual mr one can see how accurate the equation F=mrw^2 is.  In this case the slope of mass and radius is 0.117 when our actual is 0.108 which means we had a 8.3% percent error which is admittedly pushing the acceptable margin of error.

In this Force vs mw^2 graph the variable r for radius is kept constant. By comparing the slope to the actual r one can see how accurate the equation F=mrw^2 is.  In this case the slope of radius is 0.393 when our actual radius is .54 which means we had a 27.22% percent error which is too large of an error to be consider acceptable.

Conclusions:

Based on the data and graphing analysis we can conclude that the equation F=mrw^2 does indeed work. While both graphs Force vs w^2 and Force vs Rw^2 slope and actual were within acceptable percent error range the graph Force vs Mw^2 was not. This can be contributed to a number of things from random errors such as changes in voltage or the friction on the mass as it was accelerated to systematic errors suchs as inaccurate measurements or timing. If the lab were to be redone I am confident that all three graphs of data can be brought into reasonable range of percent error.

12-Oct-2016: Ballistic Pendulum

Lab: Ballistic Pendulum
Name: Andrew Martinez
Lab Partners: Richard Mendoza, Lynel Ornedo

Statement: To determine the firing speed of a ball in the spring-loaded experiment

Introduction: In this lab we will be for three things. The firing speed of the ball and to determine the trajectory the ball will travel and its landing point. Using our knowledge of potential energies, conservation of momentum, and conservation of energy we can determine all three.

Procedure:
Part 1
- Measure the length of the string holding the block in place
- Measure the height of the table
- Record the masses of the ball and block
- Place the ball into the spring-loaded gun and select which level to set it at
- Place the angle indicator at zero
- Fire the ball into the block and record the max angle
- Repeat five times
- Use the conservation of momentum to write an equation to find the speed of the system after the collision

Part 2
- Use the value gained in part one after the collision
- Use conservation of energy to and relate the max height to the initial speed of the block
- Using these value predict where the ball well land if launch from table height then find actual

Apparatus:

Ballistic Pendulum with the scale to measure mass

Measured Data
Mass_ball: 7.6 g +/- .1 g
Mass_block: 79.2 g +/- .1 g
Tables height: 85.8 cm +/- .01 cm
String length: 20 cm +/- .01 cm
Trail Angles: 17 degrees, 15 degrees, 16.5 degrees, 17 degrees, 14.5 degrees
Average Angle: (17+15+16.5+17+14.5)/5 = 16 degrees

Calculated work

Vf of mass (ball+block) = .3897 m/s
Vi of mass ball = 4.45 m/s
T = .436 s
X = 1.94 m (experimental)
X = 2.02 m (Actual)

Analysis:
Setting kinetic energy = to gravitational potential energy we get an equation which can be rearrange to solve for Vf = .3897 m/s. Using the value of Vf we relate the height to initial velocity and solve for Vi getting 4.45 m/s. We then use kinematic equations for the x-axis to find how far the ball will travel before impact and use a kinematic for the known height to find time. We get 1.94 m as the estimate range of impact. Upon actually launching we found the true impact point to be 2.02 m.

Conclusion:
This lab demonstrates how by using the laws of conservation of momentum and energy as well potential energies one can determine unknown velocities and predict there range. These estimations are reasonable accurate with a found percent error of 3.96%.