Human Power

Scott Lutes

April 16, 2013

Human Power

Purpose:

To determine the power output of a person

Equipment:

• Two-meter metersticks
• Stopwatch
• Kilogram bathroom scale

Procedure:

1. Weigh yourself on the force scale to determine your weight in Newtons
2. Measure the height of the staircase using the double-meter meterstick from the top of the second floor to the bottom of the first floor
3. Have one designated person to record time going up and down the stairs and another designated person to record the amount of time on paper
4. Compute the data you collected (weight in newtons, time to get up the stairs, time to get down the stairs) into the equation PE =mgh and Power = PE/T. This will give you the power in watts, you will need to convert that into horse-power, 1hp = 746 watts
5. Record your horse-power and present to class

Data:

Questions:

1. Is it okay to use your hands and arms on the handrailing to assist you in your climb up to the stairs? Explain why or why not.
   1. Depending on your definition on horse-power, using the stairs can can or cannot be acceptable. After looking up several definitions of horse-power, most relating to the engine of a vehicle, it is up to the person to define horse-power as the power of the entire body to run, or simply the legs of the individual to provide their movement. If you look at the entire body, than it is reasonable to assume that using the hand-railing is OK because you are determining the power it takes to get to the top of the stairs, and the more power you use, the faster you will get up, so if you are using excess power to pull on the hand-railing, it makes sense that your overall horse-power represent that.

2.) Discuss some of the problems with the accuracy of this experiment.
• Some issues with the accuracy can include miscalculation and wrong decimal placement. Odd or inaccurate reading from the force scale weight, since the weight slightly varies as you stand on it. Inaccurate measurements in accordance to the height of the staircase. Misreadings by the timekeeper can dramatically affect the results.

Conclusion:

I enjoyed this lab because we can put some of the equations we discussed and put them into real life scenarios to actually evaluate ourselves. Some of the methods used by the runners in this lab that would decrease their time actually are an accurate representation of horse-power and are not considered “cheating” as some might think. For example if you skip steps on the stairs to decrease your time, you still but an extra amount of energy to skip to that step, therefore your overall horse-power will increase. As I mentioned earlier, when you use the hand-railing to speed up your time, you still use extra energy with your arms, therefore you increase your overall horse-power.

Another aspect of the lab I found interesting has to do with weight. According to the equation, the higher your weight (or normal force) the higher your horse-power results will be according to your time. This makes sense in a physical sense because the more you weigh, the more you will have to fight to repel gravity, therefore increasing your overall horse-power.

In conclusion there are two things I will need to do to increase my horsepower, one is to run up the stairs at a faster rate, the other is to increase my general weight. This makes horse-power equivalent to the effort you put into achieving something. In determining horse-power you will have to take in to account the weight of the person or object.

Scott Lutes

April 4, 2013

Dr. Haag

Newton's Second Law

Purpose:

To study and measure the effect that forces have on the motion of a cart on a horizontal track.

Equipment:

Computer with Logger Pro software, lab pro interface, motion detector, horizontal track, cart, low friction pulley, string, paper clip weight hanger, regular weight hanger, slotted weights, triple beam balance, carpenter level, two mass bars, Microsoft Excel Software

Procedure:

1. First set everything up. Lay out the track and make sure it is leveled with the carpenter's scale. Attach the pulley system at the end of the track. Place the motion detector on the end of the track and connect it to the lab pro interface, turn on the computer and start the Logger Pro software and open it on the graphlab file. Find the combined weight of the cart and the two mass bars using the triple-beam balance.
2. Next discover the friction by placing the cart (with the two mass bars) on the track directly in front of the motion detector. Attach the string to the cart and place the other end on the low-friction pulley so it hangs off the end of the track. Than use the paper clip hanger and attach it to the end of the string at the end of the track. Add enough weight to the paper clip so when you give the cart a gentle push, it will move with a constant velocity meaning no acceleration. Record the results on Logger pro with graph lab. Once you determine that there was no acceleration in your trial, than you calculate for the friction with the equation: (mass)(gravity) – friction = (little mass +big mass)acceleration.
3. Now you will test the acceleration with different weights. Remove the paper clip hanger and attach the 50gram weight hanger to the string. Than put on an additional 50 grams (totaling to 100grams) on the hanger. Release the cart and study the results on Logger Pro. Use the quadratic fit on Logger pro in order to determine the acceleration of the cart. Repeat for a total of 5 trials, record the results on an Excel spreadsheet.
4. Than use the equation in part 1: mg – f = (m + M)a, or a = (mg – f)/(m +M) to determine your own calculated acceleration. Compare your calculated acceleration with the experimental acceleration and find the percent difference.
5. Repeat steps 3 and 4 with different masses: 150g, 200g and 250g.

Data:

Friction = (mass) * (acceleration)

F = (.00565 kg) * (9.8 m/s/s)

F = .055 N

Prediction 1 100grams	Prediction 2 150 grams	Prediction 3 200 grams	Prediction 4 250 grams
a = (mg – F) / (M+m) a = ((.1)(9.8) - .055) / (1.493 + .1) a = 0.581m/s/s	a = (mg – F) / (M+m) a = ((.15)(9.8) - .055) / (1.493 + .15) a = 0.861 m/s/s	a = (mg – F) / (M+m) a = ((.2)(9.8) - .055) / (1.493 + .2) a = 1.125 m/s/s	a = (mg – F) / (M+m) a = ((.25)(9.8) - .055) / (1.493 + .25) a = 1.374 m/s/s

Conclusions:

We ended up with some minor percent error's that was most likely due to a slight miscalculation in the friction. The most difficult part of the experiment was to find the friction. It is difficult to find an exact mass for the cart to have a constant velocity. If we used a slightly different weight, our calculation for friction would be off, since the friction is used on all of the calculations to discover the acceleration, One minor mistake in determining our friction would result in a miss-estimate to find a predicted acceleration. Our percentage difference included a maximum of 13% and a minimum of 3%, resulting in a total average of 8.2% error. I believe this was mostly due to our calculation error rather than the experimental error because the most difficult part was left to us to find the friction, and the experimental results were mostly taken from the machine tools we used including the motion detector and logger pro, and though these tools are not perfect, they will most likely conclude a better result than we can to find an appropriate weight to calculate friction. I did notice that the more weight we we added in the experiment the lower our percent difference was. We started off with 100g and and got a 13% difference in the predicted and experimental results. We ended with 300g and received a 3% difference between the two results. I have concluded that there is less room for error as the weight becomes more significant because our results become more exact as the weight increases. For instance it is easier to calibrate a scale with a 100g weight than it is with a 0.1g feather.

In our experiment we over-estimated our acceleration each trial. I have come to realize that if you over estimate the friction, you will under-estimate the acceleration. In our case we under-estimated the friction so our acceleration was over-estimated. This is discovered by simply looking at the equation: a = (mg – f)/(m +M), the higher the friction, the lower the numerator will become thus the lower the acceleration becomes.

In conclusion, we should have taken more time determining the friction in step number two. We should have carefully evaluated the friction between a spectrum of different weights in order to find the one resulting in the least amount of acceleration. Though we did study several different weights, we could have been even more precise up to the last fraction of a gram.

 

 

Working with Spreadsheets

Scott Lutes

20 February 2013

Dr. Haag

Physics 4A

Working with Spreadsheets

Purpose:

          To be familiar with entering and computing data on an Excel Spreadsheet, using equations and other given information

Equipment:

• Computer with Microsoft Excel software and Graphical Analysis software

Procedure:

          Turn on the computer and open Microsoft Excel. In different columns type: x, f(x), amplitude, frequency and phase. Amplitude is equal to 5, frequency is equal to 3 and phase is equal to (PI/3); place these values below it's respective title. For the “x” column, type “0” directly below and continue incrementing the values by .1 below until you reach to 10. For the f(x) values, you will plug in the equation “A sin(Bx+C)” under the f(x) column. Instead of typing in the equation, you will have to use the given values for each variable, so for A click on the square that contains the Amplitude value, for B click on the square that contains frequency value and for C click on the square that contains the phase value. Notice that the variables A, B and C remain constant, while the x value gradually increases. In order to accommodate the constants to not change, use “$” between the block column name and the block row name. Once you type in the equation, drag the equation down to all the rows consistent with the “x” column. The f(x) will provide you with an answer for each corresponding “x” value. Finally you will copy and paste the x and f(x) values onto the Graphical Analysis software under the “X” and “Y” table to make a graph of the function.

          After you finish you will repeat the steps for a different set of data: g = 9.8m/s/s, v initial = 50m/s, x initial = 1000m with an increment of .2 seconds using the equation “A+Bx+Cx^2”.

Data:

          All of our data was done on a Microsoft Excel Spreadsheet and Graphical Analysis software posted and attached with this blog below:

                                                              

Conclusion:

          My partner and I figured out that we can easily calculate an equation from given variables and constants on an Excel Spreadsheet. Excel is like a Microsoft calculator that easily interprets data and determines a result based on your computation, your data, and your equations. Now for future experiments and labs we can easily enter our data into an Excel Spreadsheet and let the program compute the results. This minimizes human error in computation and leaves the hard part for the computer program. Also with the data readily available on the computer, we can easily transfer our data onto the Graphical Analysis software like we did in this lab. We than can view our results in a much more time efficient way.

          The difficult part of this lab was correctly entering the equation. The downside for the program was that there were various symbols that pertain to the program that the user might not necessary be familiar with, and it might take some research to find out. In this case we had to use the symbol “$” to identify unalterable constants while leaving the rest of the variables that change alone. We wouldn't have known to use this symbol if our teacher hadn't told us, otherwise we would have been searching for it online.

          Once we copied and paste our data onto the Graphical Analysis software we got an accurate position graph of the particle in motion. To make sure the graph was accurate, we highlighted a certain portion of the graph and clicked on analyze to let the software provide us with the given variables involved in the equation. We ended up with the values: a = -5, b = 3, and c = -14.7. Our given values were originally a = 5, b = 3 and c = (PI/3). The “a” became -5 because the portion of the graph we highlighted included the bottom of a parabola rather than the top. We immediately realized that the amplitude goes up and down in a sin graph so with a given amplitude of 5, the amplitude would either be – or + depending on which portion of the graph we highlight. The phase was off as well for the same reason, the sin graph infinitely continues in the x direction so depending on where we highlighted our graph we would receive different results. 

Acceleration of gravity

Today in class we did a lab to portray the acceleration of gravity in real life scenarios. We had a motion detector which we placed on the floor and covered it with a protective cage. We then held a ball directly above it and tossed it into the air and let it fall. The motion detector would then record the motion of the ball and graph it on a computer. From the results we can gather a position graph as well as a velocity graph.

Why should it be a parabola?
The position graph looks like a parabola because it is tracing the motion of the ball over time. Since a ball goes up and down so does the parabola over time.

Why does the curve have a negative slope?
The curve has a negative slope because the velocity is always negative. Since gravity always pulls the ball down, as soon as it leaves someone's hand, the velocity is always negative from that point.

What does the slope of this graph represent?
The slope of the graph represents the velocity. It represents the position divided by the time which is equivalent to velocity.

Graphical analysis lab