Download Chapter 4 Mass of Car Lab

Physics--Chapter 4: Forces and the Laws of Motion
Mass of a Car Lab
Title: Finding the Mass of a Car
Date:
Partner(s): our whole class
Objectives: Using Newton’s second law, we will experimentally determine the mass of a car (yes, a real
car!).
Materials: car, 2 force plates, LabPro w/ batteries, TI 84 Plus SE calculator, link cable, track measuring
tape, 10 orange cones, stopwatch
Procedure:
1) Connect the force plates to Channel 1 and Channel 2 of the LabPro. Open Easy Data and clear the
program. Force plates will auto I.D. Holding the force plates by the attached handles (attach
handles if they are not already attached) vertically upright, zero the force plates.
2) Find the force of friction of the car while being pushed. Designate two people to push the car
throughout the lab. Having the same people will increase accuracy since they will get better at the
technique used to push the car. The Ff can be found by having the “pushers” push the car so that a
constant velocity is achieved for the length of the parking lot. Place the force plates on the back
window of the car and push the car just enough to keep it moving. Another student should walk
along with the LabPro to monitor/collect force data. Those students who will be riding in the car
(the driver, the timer, and the cone-dropper) should be riding in the car while this is done. Pushers
should maintain a slow, steady, velocity and constant force while doing this. When satisfied with
the value obtained for the force of friction, Ff, record this value in your data table. Note that we are
using 2 force plates (so values of each should be added together)!
3) Find acceleration and applied force. The pushers will decide on a force to push the car at to achieve
an acceleration. It is important that the force used is maintained throughout the trial. The timer
will say “go!” and the timer will start the stopwatch and the pushers will begin pushing all at the
same time, with the force monitor walking along with the pushers. Every 3 seconds, the timer will
indicate to the cone dropper to drop a cone out the window of the car. This will be repeated until
all 10 cones are used. As the cones are being dropped, the distance between the 1st and 2nd cone,
the 2nd and 3rd, cone, etc. can be measured with the track tape. The force the pushers used and
distance between successive cones should be recorded in the data table. The total mass of
everything and everyone in the car when the data was collected should also be recorded in the data
summary as “extra mass”.
4) Repeat to collect data for a second and third trial.
Data Summary:
Trial #:______ Fapplied:______________ Ff:_______________ Extra mass:__________
Cone Interval
1-2
2-3
3-4
4-5
5-6
6-7
7-8
8-9
9-10
Interval Distance (m)
Interval Time (s)
Interval Speed (m/s)
Elapsed Time (s)
Physics--Chapter 4: Forces and the Laws of Motion
Mass of a Car Lab
Trial #:______ Fapplied:______________ Ff:_______________ Extra mass:__________
Cone Interval
1-2
2-3
3-4
4-5
5-6
6-7
7-8
8-9
9-10
Interval Distance (m)
Interval Time (s)
Interval Speed (m/s)
Elapsed Time (s)
Trial #:______ Fapplied:______________ Ff:_______________ Extra mass:_________
Cone Interval
1-2
2-3
3-4
4-5
5-6
6-7
7-8
8-9
9-10
Interval Distance (m)
Interval Time (s)
Interval Speed (m/s)
Elapsed Time (s)
Results:
1) For each trial, plot interval speed vs. elapsed time to obtain acceleration. Use a graphing calculator.
Give the slope for each of your graphs and the correlation value. The slope is your acceleration.
2) Use the values obtained for Fapplied and Ff to find Fnet.
3) Use your results to #1 and #2, and the extra mass to find the mass of the car.
4) Use your own words to relate Newton’s second law to this lab.
Conclusion: (refer to your laboratory report guide sheet)
Discussion of Error: Obtain the theoretical mass of the car and find a percent error for the average of
your result. Discuss accuracy using this value, and using your three trial values, discuss precision.
Suggestions for Improvement: (always make a reasonable suggestion!)