Joyce FielSeptember 25, 2007

AP Physics 1º

Lab #2- Acceleration and dvt

PUPOSES:

1. To find and understand the relationship between displacement, velocity, acceleration, and time2. To better understand the equation s= ½ at2

3. To calculate displacement, acceleration, velocity, and time4. To see how slope affects displacement, acceleration, velocity, and time5. To record and compare different dvat statistics for different things with wheels6. To see and understand how the experimental variables affect the data7. To use teamwork to get through the lab as efficiently as possible

APPARATI:

Material Qty. Material Qty. Material Qty. Material Qty.Gentle hill 1 Skateboard 1 Bike 1 Stopwatch 1Meter stick 1 Scooterskate 1 Rollerblades 1 Chair 1Tape 1 Razor Scooter 2 Tricycle 1 Stroller 1

THEORY:

Kinematics: study of how objects move Average velocity= displacement/ time Average acceleration = change in velocity/ time Displacement= object’s change in position Time is the independent variable Slope affects velocity and acceleration

PICTURES:

more on next page

METHOD:

Before the day of the lab, Elizabeth and I discussed what rolling objects we would bring to the lab and we decided on a skateboard, rollerblades, a wagon, and scooterskate. Elizabeth, Sarah, and Leslie also discussed the lab materials on Friday when I wasn’t there. This is our procedure on day one of the lab

1. Obtained materials and walked to the hill2. Decided that the finish line would be where the wall of the C building was perpendicular to the ground,

making a 90º 3. Marked the finish line with thin masking tape that kept ripping4. Used the meter stick to measure 5 meters from the finish line and used tape to mark the 5 meter line.

Class could’ve done this more productively because our class was pretty much divided into two groups. One of the groups started measuring from the top of the hill. If they had worked with us, we could have divided and conquered and finished faster. We wasted a lot of time setting up that day.

5. Used the meter stick to measure 5 meters from the 5 meter line to make 10 meters from the starting line6. Used the meter stick to measure 10 meters from the 10 meter line to make 20 meters from the starting

line. Measuring wasn’t very accurate because we had to keep moving the meters stick so it probably wasn’t exactly 5, 10 and 20 meters.

7. Experimented with the scooter at the 5 meter line first. Team experimented each object at each distance 3 times

8. THE TEAM: Designated rider: Joyce (me), timer: Sarah, recorder: Elizabeth, photographer: Leslie9. Experimented with the bike, rollerblades, scooterskate, and skateboard at the 5 meter line10. While experimenting, the team took record of all experimental variables. If they got in the way too much,

the team neglected the data and did a redo. Some things that caused redos were running into a wall, stopping abruptly because of someone being in the way, rocks and pebbles that significantly changed the velocity of the ride, too long of a time to start riding down the hill (this happened a lot with the scooterskate and the rollerblades)

11. With some of the objects, the rider had to lean forward in order to change the center of gravity to get the object to move faster (happened a lot with the scooterskate and rollerblades)

12. Experimented with bike at the 10 meter line13. In the experiments the timer started timing as soon as the front wheels touched the tape of the starting

line and stopped timing when the front wheels touched the tape of the finish line. 14. The first day timer would see for herself when it was time to start and stop timing and the rider would

helpDAY 2

15. Course already setup, no additional setup was needed16. Measured slope (rise/run) of the hill by the marks on the wall and the distance of the course 17. The team came equipped with a camera and more objects to experiment with. The jobs remained the

same18. Experimented with the same objects at the 10 meter line then the same objects at the 20 meter line19. Altered timing method—this time the recorder called go when the front wheels touched the tape of the

starting line because the timer had to stay at the finish line to see when the front wheels would touch the finish line

20. Attempted to experiment with a rolling office chair, tricycle, and a stroller but it was to difficult to get them to even start rolling down the hill

21. Experimented with skateboard standing up instead of sitting down at 5, 10, and 20 meter distances22. Experimented with bike with one foot on the pedal and a knee on the other so the rider wasn’t sitting

down23. (Photographer took pictures of each run)

DATA TABLE:

Object Distance Trial I time (s) Trial II time (s) Trial III time (s) Average Time (s)*Bike (sitting)

5m 3.82 3.59 3.66 3.6910m 5.69 6.37 6.00 6.0220m 10.19 10.31 9.44 9.98

Bike (standing)

5m 3.52 3.72 4.03 3.7610m 5.78 5.59 5.50 5.6220m 8.34 10.22 9.10 9.22

Scooter 5m 4.75 3.34 4.38 4.1610m 5.91 5.56 6.12 5.8620m 9.88 9.87 9.38 9.71

Rollerblades 5m 10.19 9.16 13.50 10.95 **10m 11.53 11.09 9.78 10.80 **20m 19.28 20.31 20.09 19.89

Scooterskate 5m 8.43 9.09 7.97 8.4410m 15.03 13.69 12.91 13.8720m 19.65 20.09 13.07 17.60

Skateboard (sitting)

5m 4.28 4.31 4.25 4.2810m 6.44 6.41 6.44 6.4320m 10.44 10.04 10.57 10.35

Skateboard (standing)

5m 4.19 4.31 4.46 4.3210m 6.68 6.25 6.37 6.4320m 11.53 11.38 10.84 11.25

Slope 40.5cm/20.1m

ANALYSIS:1) Calculations

Velocity= distance/ time *in this case , average time from the table above is used for time Average time= (time1 +time2 + time3)/3 In this case, distance= displacement because motion only went in one direction

OBJECT DISTANCE VELOCITY OBJECT DISTANCE VELOCITY OBJECT DISTANCE VELOCITY Bike (sitting)

5m 1.36 m/s Roller-blades

5m 0.46 m/s Skateboard (standing)

5m 1.15 m/s10m 1.66 m/s 10m 0.93 m/s 10m 1.56 m/s20m 2.00 m/s 20m 1.01 m/s 20m 1.78 m/s

Bike (standing)

5m 1.33 m/s Scooter-skate

5m 0.59 m/s10m 1.77 m/s 10m 0.72 m/s 20m 2.17 m/s 20m 1.14 m/s

Scooter 5m 1.20 m/s Skate-board (sitting)

5m 1.17 m/s10m 1.71 m/s 10m 1.56 m/s20m 2.06 m/s 20m 1.93 m/s

Acceleration= change in velocity/ time elapsed Change in velocity= velocity20m-velocity5m

In this case time will be the average of the 5, 10, and 20 meter times Time elapsed =( time5m + time10m + time20m) / 3

Object Change in velocity

Elapsed time

Acceleration

Rollerblades 0.55 m/s 13.88 s .040 m/s2

Scooterskate 0.55 m/s 13.30 s .041 m/s2

Skateboard (standing) 0.63 m/s 7.33 s .086 m/s2

Bike (sitting) 0.64 m/s 6.56 s .098 m/s2

Skateboard (sitting) 0.76 m/s 7.02 s .108 m/s2

Scooter 0.86 m/s 6.58 s .131 m/s2

Bike (standing) 0.84 m/s 6.20 s .135 m/s2

2) Line Graph

5m 10m 20m0

0.20.40.60.8

11.2

Rollerblades

Series1

distance (m)

velo

ity (m

/s)

5m 10m 20m0

0.5

1

1.5

2

2.5

Bike (standing)

Series1

distance (m)

velo

city

(m/s

)

rollerblad

es

scooter

skate

skateb

oard (st

anding)

bike (s

itting)

skateb

oard (si

tting)

scooter

skate

Bike (s

tanding)

00.060.12

Accelerations

Series1Series2

object

acce

lera

tion

(m/s

2

3) Questions What were the independent and dependent variables?

The independent variable was distance (and in this case displacement also) and the dependent variable was time. Acceleration and velocity were things that were derived from both.

What were some experimental variables?Some experimental variables were rocks on the ground, people and objects in the way, the consistency of the timer, the consistency of the rider (was she doing the same thing for every trial?), the direction the rider traveled to the finish line (straight line or diagonal line?), if the rider was leaning or not, if the rider pushed off, etc.

Which objects had the fastest and slowest velocity?Order of objects from least to greatest velocity (with respect to the 20m displacement): Rollerblades, scooterscate, skateboard (standing), skateboard (sitting), bike (sitting), scooter, and bike (standing)

Which objects had the most acceleration?Least to greatest: Rollerblades, scooterscate, skateboard (standing), bike (sitting), skateboard (sitting), scooter, and bike (standing)

RESULTS: 1) The data and the calculations derived from the data indicate several things. The greater the displacement,

the higher the velocity. The velocities of the 20 meter distances were greater than the velocities of the 5 meter distances. This is due to the slope of the hill and acceleration. Because the object starts at a greater distance, it can accelerate more because the hill has a slope. The data also shows that the rider had the highest velocity when she was riding on the bike. That is probably because she was leaning forward so her center of gravity shifted towards. The object with the slowest velocity was the rollerblades. That was probably due to old wheels. The object with the highest acceleration was also the bike standing up and the object with the lowest acceleration was, again, the rollerblades.

2) Personally, I think or team accomplished 6 out of 7 of our objectives. We did understand the relationship between displacement, velocity, acceleration, and time. Time was the independent variable that affects displacement, velocity, and acceleration. The greater the time, the greater the displacement. The greater the displacement, the greater the velocity, and the greater the velocity, the greater the acceleration (in this lab at least). The one objective I don’t think we accomplished is to fully understand the equation s= ½ at2. Although we listed it as an object from the very beginning. We didn’t really try to illustrate it during our experiments. We did find time by using a stopwatch, even though it wasn’t standardized and

displacement was a standard. We were able to calculate velocity and acceleration as shown in the data tables above. We also were able to record and compare different dvat statistics for different things with wheels. Variables that affected the lab were taken note of and the team was able to recognize the effects they had. Rocks significantly slowed down the object, not traveling in a straight line to the finish line increased the time, etc. I think we accomplished the second objective better on the second day because everyone was already familiar with what they had to do and we didn’t waste anytime.

3) Our group distinguished ourselves by bringing a lot of objects to test. We were the only people who brought chairs, a tricycle, and a stroller. Even though it didn’t work because the wheels were shabby, I think we should get credit for trying to go above and beyond the normal skateboards, bikes, and scooters. Our group also brought rollerblades and a scooterskate and I think we tested the most objects out of everyone else. In addition, we tested two objects twice in different ways. I think we were also the only group to remember to get the slope and we were the group who began setting up the track in the right place. I think we also distinguished ourselves by making our instructor laugh. This lab got me to look at what increases acceleration and velocity in two ways. At first I thought that the greater the distance, the faster the velocity should go, but this lab made me realize that it would also make sense if the shorter the distance, the greater the velocity. For example, if there was a very steep slope and we had to start 5 meters from the finish line, that would be where the slope is the steepest so it would make sense for it to go faster there since the steeper the slope, the greater the velocity. I think this is because when the slope is steeper, it’s closer to being vertical so gravity is pulling on it more and it accelerates more and the acceleration, in turn, increases velocity. If we had more time, I would have liked to test from an even farther distance away from the finish line, say maybe all the way from the top of the hill. I would also like to test on a steeper slope so I could compare the data and see exactly how numerically the slope affects the speed.

PICTURES: