constantmotionlab

Exploring Constant Speed of Crash Carts
Ivy Armstrong
With Partner: Brianna Mack
Purpose: To explore the constant speed with crash carts by finding the speed of a crash cart in
more than one trial. Within our experiment we will try to send the cart at different speeds to
explore the consistency of speed within each trial.

Procedure: 1. Obtain ticker tape, crash cart, carbon disk and ticker timer from teacher.
2. Attach ticker tape to the rear bumper of the crash cart and set up ticker timer with carbon disk.
3. Push the crash cart so it maintains a constant speed. 4. Repeat 11 times with a fresh piece of
ticker tape. * Make sure to label each piece of tape with the trial number so that no confusion is
possible. 5. Count 6 dots and measure the distance between the 1st and 6th in order to calculate
the speed of the cart. * Make sure this is done for three different 6 dot areas along the piece of
ticker tape for each trial.

Data:

Trial Number    First 6 Dot Section
Distance (cm)    Second 6 Dot Section
Distance (cm)    Second 6 Dot Section
Distance (cm)
1    11 cm    10.35 cm    10 cm
2    20.45 cm    18.6 cm    18.6 cm
3    6 cm    5.75 cm    4.5 cm
4    16 cm    15.55 cm    15 cm
5    30.5 cm    29.75 cm    27.5 cm
6    5.1 cm    5.95 cm    5.5 cm
7    2.75 cm    2.4 cm    3.2 cm
8    26.15 cm    24 cm    25.1 cm
9    6.45 cm    6 cm    5.15 cm
10    19.25 cm    18.85 cm    18.5 cm
11    51 cm    23 cm    NA

Questions:
1. Why do we disregard the 1st small length of the tape?
The first section of tape is disregarded because it is the area where the dots are from before the
cart is moving and as it is quickly accelerating to the constant speed.

2. What do evenly spaced dots on the tape mean?
Evenly spaced dots show us visually that the speed of the crash cart is approximately constant
which is why we take the measurements in this area to determine what the constant speed is.

3. What do dots getting farther apart mean?
When the dots are getting farther apart it means that the cart is getting faster and thus the tape is
moving faster making less dots per area.

4. After the push, what forces acted on the cart and how large of the forces (large, small, almost
nothing)?
When the cart is pushed the force of the friction against the ground affects the cart. This force is
a moderate force. Also, there is a gravity forces upon the cart. The ticker tape also makes a
slight force causing the cart to slow down a little.

5. What can you claim about the speed of the cart after the initial push?
The push causes an acceleration until the cart reaches a constant speed. This speed will maintain
its self for a certain amount of time before it gradually slows down.

6. What have we proven? Explain.
This lab has proven that after an initial acceleration the speed of the crash cart remains basically
constant for a great amount of time before deceleration. This is proven through the averages of
the distances on the ticker tape and the speeds we have calculated.

Sample Calculations:
To Change from cm for 6 dots to cm/s:
10 cm/(1/10 s) = 100 cm/s

To change from cm/s to km/hr:
100 cm/s * 3600 s/hr / 100000cm/km= 3.6 km/hr

To find the average of the speeds:
3.96 km/hr + 3.726 km/hr + 3.6 km/hr = 11.286 / 3 = 3.762

    Table of Results:
Trial Number    First Calculated
Speed in Km/Hr    Second Calculated
Speed in Km/Hr    Third Calculated
Speed in Km/Hr    Average
Speed
Km/Hr
1    3.6     3.726    3.6     3.762
2    7.362    6.696    6.696    6.918
3    2.16    2.07    1.62    1.95
4    5.76    5.598    5.4    5.586
5    10.98    10.71    9.9    10.53
6    1.836    2.142    1.98    1.986
7    .99    .864    1.152    1.002
8    9.414    8.64    9.036    9.03
9    2.322    2.16    1.854    2.112
10    6.93    6.786    6.66    6.792
11    18.36    8.28    NA    13.32



Sources of Error:
The floor may not have been completely level which may have caused the cart to speed up and
slow down erratically. There may have been inaccuracy within the measuring device.

Conclusion:
The data shows that when calculated in km/hr the average of the three sections is favourably
similar towards the data and there is not a huge gap of difference in most cases. The speed of
the cart within each trial was relatively constant within the experimental error. We have shown
that it doesn’t matter what the speed of the cart is the speed should remain relatively constant.

Further we could prove this more certainly if we had an apparatus which would send the cart at a

constant speed all the time. This would prove with several trials that the speed will remain
constant.