friday practice

Friction Lab

Experiment 1 Surfaces Pressed Together

Pre-Lab Questions

1. How is the friction force affected when the surfaces are pressed together more? 

Prediction: When there is more weight added in order to manipulate the normal force, the force of friction increases. 

IV: Normal Force 

DV: Force of Friction

CV: Velocity, Surface Area

Secondarily experiment: change of surface material: rubber/felt 

Apparatus: 

List of equipments

Surface (table)

Block 

Computer 

Dual Force Sensor

Masses

Procedure:

We attached the block to the Dual Force Sensor and started pulling it with our hands at a constant speed. We executed the process by adding different weights on the velcro sided block to see how it would affect the force of friction between the table and the material. The Dual Force Sensor measured the amount of Ff, while the weights determined the Fn. Because it is being pulled at a constant speed, the Ff and Fnno Ff and the pulling force are equal are equal. The powers of the machine have to be equal because the block is moving at a constant speed.We changed the material of the block by experimenting once with velcro and once with the rubber side. We repeated the procedure the second time, but changed the side of the block so it was the table against the rubber surface.



Data Table

Velcro:
Fn (Newtons) Ff (Newtons)
0.64 N 0.16 N
1.13 N 0.24 N
1.62 N 0.36 N
2.60 N 0.45 N
5.54 N 0.86 N
8.33 N 1.38 N

Rubber:
Fn (Newtons) Ff (Newtons)
0.64 N 0.46 N
1.13 N 0.68 N
1.62 N 0.76 N
2.60 N 1.19 N
5.54 N 2.78 N
8.33 N 4.29 N

VM: As the Fn increases, the Ff increases constantly. Normal force -is this stella's graph?

MM: Ff=(0.2 N/N)xFn+0.07N

Slope: For every 1 Newton added to the normal force, the force of Friction increases by 0.2 N.

Y-int: When the Fn is at 0 Newtons, the Ff is at 0.07 N. 

VM: As the Fn increases, the Ff increases constantly.
MM; Ff=(90.5 N/N)x Fn+0.02N why does it say 90.5?
Slope: For every 1 N added to the Fn, the Ff increases by 0.5N.
Y-int: When the Fn is at 0 N, the Ff is at 0.02N.



Experiment 2 Velocity
2. How does the velocity affect the Ff?

Prediction: As the velocity increases, the force of friction decreases.

IV: Velocity
DV: Ff
CV: Fn, Surface materials

Procedure
We pulled the block at different speeds: slow, medium, fast. We were able to measure the different velocities with the Dual Force Sensor, and determine the relationship between the velocity and Ff.

VM: As the different speeds are applied, the Force of friction remained the same.

Experiment 3 Surface Area on Ground
How does the surface area affect the Force of friction?

Prediction: The bigger the surface area, more Force of Friction is present.

IV: Surface Area
DV: Force of Friction
CV: Speed and Surface Material

Secondary Experiment: Change the side of the block.no secondary here -you changed the side of the block to manipulate the surface area

Procedure
We measured the Force of Friction using a piece of wood and used all the different sized surface areas. We made sure the the speed and the surfaces remained the same in order for our experiment to be as accurate as possible.

VM: The surface area does not affect the force of friction.

where is the graph from schoology?
Conclusions

Introductory Paragraph
Through these series of experiments, our goal was to determine the relationships between the surface area, velocity, and force of friction. We were able to find out that the only factors that have an affect on the friction is Fn and surface. Throughout the three experiments, we kept the surface constant in all three of the experiments. We changed the the Fn, velocity, and the surface area in order to find out how they affect the force of friction.

Experiment 1
According to our first experiment, all of the graphs are linear because of the same slope. The slopes are the same because the same surface was used. The velcro side was 0.2 N/N while the rubber side was 0.9 N/N. The slope of the velcro side was less, because there was less friction against the surfaces. By adding weights, it shifted the graphs but they still remained proportionally the same. The slope also remained the same. We concluded that as the Fn increases, so does the Ff.What is the equation?  What do we call the slope?

Experiment 2 & 3
We were able to find out that the velocity and the surface do not have an affect on the Ff. The Ff will continue to remain the same if and only if the Fn and surface stay constant. The change in velocity or surface are do not affect the force of friction. My group predicted that the bigger the surface area, the bigger Ff would be. Our prediction was wrong, as we concluded that it does not affect the relationship whatsoever.

Drawing Conclusions
It is possible for two people wearing identical shoes to have different forces of friction. The material of the surface they are standing on and their Fn would be factors that could affect the Ff. The different surfaces could have affect the friction, based on whether the surfaces would have less or more friction. For example, tile floors would have less friction than carpet. The weights of the individuals also have an affect on the forces of friction. Based on our first experiment, it was proven that the more Fn applied, the more Ff would be present. If one of the people weighed more, that person would have more force of friction. The only way the forces of friction could be equal is if they both weigh the same and are standing on same surface material. The surface area and velocity would not change the force of friction.

Errors
For next time, we could be more careful and take more accurate data. An error that occurred during our experiment was when we failed to zero the program, resulting in data that was not accurate. If we knew what we did wrong during that time, we would have saved time and extra work. Thankfully we were able to fix the problem before it was too late.

Journal Statement
After completing the lab report, I felt more confident in my lab skills. I understood the concept and what we were trying to achieve in the experiment. Through this lab, I understood how to determine the relationship between 2 or more factors by changing variables and keeping one constant. In order to improve the experience, we could pay closer attention to what kinds of data we were collecting and ask questions if conflicts arose.good!

Gravity

Graph

Analysis
VM: As the mass increases, the force increases.proportionally
MM: y=9.7045x+0.0122
Fg=(9.7045N/kg)M
Fg is force of gravity.
M is mass.
(9.7045N/kg) is g:gravitational field strength on earth. 

Slope: 9.7045
what increases> increases by 9.7045units? per every kg

Y-int: 0.0122
y-intercept is almost 0 because there is 0 force at 0 mass units??

Data Table too many decimal places....

Mass (kg)	Force (N)
0.060000 kg	0.581000 N
0.100000 kg	0.980900 N
0.150000 kg	1.473000 N
0.250000 kg	2.456000 N
0.550000 kg	5.342000 N

Conclusion/Evidence/Claims

Mass and weight differ because weight is the force of gravity while mass is the amount of stuff in something. Everyone's graphs are the same because we all got almost 9.8 as the gravitational field strength on Earth. All graphs are linear with the same slope, traveling in a positive direction.  nothing is traveling, it;s a different relationship The field is the same because the gravitational field remains the same no matter where you are on Earth. good!Our new equation was Fg=mg, which we got by multiplying the mass by the gravitational field strength, and therefore you get the total force of gravity. F is the force of attraction between the two objects. G is the universal gravitational constant. M is the mass of the objects.

Greater the mass, the more weight will be on the object. good!

Bonus:

Light and heavy objects hit the ground at the same time when dropped because 

No matter the size, a big object's Fg/mass will be the same as a small object's Fg/mass.  excellent!

The Moon Lab

To calculate the distance between the Earth and the moon, we had to follow several steps. First, we found the distance between the earth and the moon which is 238,900 miles or 384,400 km. Then, we calculated how many earths is earth away from the moon. It takes 30 earths to get to the moon. Afterwards, we calculated the proportions of our "earth" and "moon."

Earth was 16 in
Moon was 4 inches
So then we measured boards and laid them across the classroom, which will be made up of diamter "earths".
In the solution, we came to the conclusion that the distance between the Earth and the moon consisted of 30 earths, or approximately 480 inches.

Dueling Buggies Lab

Objective Statement
The problem we were trying to solve was to come up with a way where we could calculate where the two cars, with different velocities, coming from opposite directions would meet. To find out the position and the time of the collision, we needed to either come up with an algebraic equation or solve it graphically. To do so, we needed to collect our measurements and calculate the different variables that would make up the formula needed to solve our problem.

Your Plan

What we did was we found the average velocities of both of the buggies. Because one was faster than the other, we ran 2 trials.

1. Aligned 2 rulers after each other, with the overall length of 80 inches. 
2. Marked every 10 inches the rulers.
3. Placed the buggy at 0 inches. 
4. Once the buggy would start traveling, we started the stopwatch.
5. With the stopwatch, we timed how many seconds it took for the buggy to reach the markings at 10 inches. 
6. After recording down the relatively close times, we calculated the average of all of them (7-8 for each buggy) to get the most legitimate time. 
7. Plugged our results into Velocity=Distance/Time formula to calculate speed. 
8. Repeated the process for the 2nd buggy. 

To calculate the average, we added all of the time measurements together and divided by how many measurements there were recorded. To convert our sec per 10 inches to velocity, we divided the time by distance. By doing so, we found the rate for both of the buggies.
Calculations
1st buggy
10in/1.84sec= 5.43in/sec

2nd buggy
10in/0.46sec=21.74in/sec
distance/time = speed ... I need to see those calcualtions

From the data we collected, it was evident that the 2nd buggy was much faster than the 1st buggy because it took the 2nd buggy 4 times as fast to reach the 10 inches compared to the 1st buggy. 

Data Analysis

After a long time of not figuring out how to connect the information to solve our problem, we finally reached a conclusion. Since the problem included rate, time, and distance, it occurred to me that we could use the rate times time = distance formula. Therefore I tried an equation we usually see in our math books in a word problem: (rate and time of the first buggy) plus (the product of rate and time of the second buggy) which would equal the overall distance. With the lab, the equation looked a little like this: (5.43t)+(21.7t)=the given distance.  Adding these 2 equal the total distance because the amount they both traveled equal the total distance. (5.43t) is the amount of distance the first buggy traveled, and (21.7t) is the amount the second buggy traveled until the collision. You need the total distance to calculate the collision point. WHY does adding these 2 equal the total distance...  this is important to explain - 5.43 is the rate of the first, slow buggy, while 21.7 is the rate of the faster buggy. 

ok good!  :)

Buggy #1	Buggy #2
1.90 sec/10 in	0.38 sec/10 in
1.95 sec/10 in	0.41 sec/10 in
1.68 sec/10 in	0.40 sec/10 in
1.9 sec/10 in	0.48 sec/10 in
1.76 sec/10 in	0.52 sec/10 in
1.93 sec/10 in	0.55 sec/10 in
=1.83 sec/10 in	=0.46 sec/10 in

Model/Designing a Solution

With our formula, we would be solving how many seconds it would take for the two buggies to collide. With the given distance of 65, we plugged it into the equation                 (5.43t)+(21.7t)=65 to get an answer of 2.4 seconds. Then, we ran a trial run with the stopwatch and it took exactly 2.4 seconds for the cars to collide at 17.5 inches, meaning our method was successful. 

The Buggy Lab

The Buggy Lab

Pre-Lab Observations

• Stays in straight line 
• Makes noise 
• Has lights flowers
• Wheels 
• Red 
• Forward only
• Keeps going 
• Two seats 

Objective

The objective of this experiment is to interpret the change in position vs time of the buggy with a graph. By following the simple procedure steps, we will be able to see if there is a pattern visible in the trials. We will be able to understand the concept of motion and velocity more clearly. good

• Collect and organize data of the car’s motion. 
• Create a position vs. time graph using data collected. 

Procedures 

• After carefully aligning the rulers after each other,  we measured how far the car is able to travel from 0 inches,  every 2 seconds. We marked the buggy's position with tape wherever the car was every 2 seconds. By doing so, the floor was filled with tape marks that were separated by roughly the same distance from each other. In the second trial, we changed the direction the car was going. We started the car from the endpoint of the first trial and repeated the process, but going backwards. 
• By marking the position of the buggy, we were able to record the constant increasing position of the car. This proved that the speed was always constant and we were more likely to find a pattern. 

Data 

Trial 1                                                 Trial 2

Time(sec)(x)	Position(in)(y)
2 sec	37 in
4 sec	83 in
6 sec	121 in
8 sec	152 in
10 sec	178.2 in
12 sec	208 in

Time(sec)(x)	Position(in)(y)
2 sec	208 in
4 sec	177 in
6 sec	151.7 in
8 sec	119 in
10 sec	86 in
12 sec	34.5 in

Data Analysis
Trial 1

y=16.75x+12.667

Position=(16.75in/sec)time + 12.667 inches
VM: As the time increases, the position increases consistently.   (time vs position)
Slope: For every 1 second the buggy's position increases by 16.75 inches.
Y int: When the position is 0 inches, the time is 0 seconds.

Trial 2 

y=-16.22x+244.19

Position=(-16.22in/sec)time+244.19 inches
VM: As the time increases, the position decreases consistently. (time vs position)
Slope: For every 1 second, the buggy's position decreases by 16.22 inches.
Y int: When the position is 208 inches, the time is 0 seconds.
excellent!

Conclusion:
Claims/Evidence

1. The speed of the buggy is never-changing, therefore based on the graphs, the distance between the positions are roughly the same. (Slopes are roughly the same) 
2. To compare two or more theses, you need to have at least one constant variable that will never change and another variable that is different. In this case, the speed and time were always the same, while the direction/position were different in trial 2. time wasn;t the same was it?  if time was same, how could position be different?
3. Based on the two graphs, no matter what the position or which direction the buggy is traveling, the slope is not going to be affected as long as the velocity remains the same. Although the first linear graph had slanted right line and the second graph had a slanted left line, the positions were roughly the same(just opposite bc of the direction). 
4. what dos y-intercept tell you?

Errors

• Something we could do better next time as a group includes paying more attention to our measurements and the objectives. In our first trial, we didn't make sure the all the rulers were measuring the same unit. Because some of our measurements were in inches and others in centimeters, our graph was off but we were able to catch our errors and fix them before it was too late. yikesAnother thing we could do is use other advanced tools to get more of exact measurements. 

After completing this experiment, I have concluded that physics includes a lot of hands-on activities, with graphs, trials, and experiments. This wasn't the most exciting experiment for me, but served as a good fundamental first step to the basic concepts of physics.  agreed.  It will get more involved and hopefully provide more challenge for you!

And remember to invite me again so I can answer in my work email.  Nice work!