Free Fall Ticker Tape Lab
Objective:
1) Provide Evidence using a strobe photo, distance vs time graph, velocity vs
time graph, and calculation that a dropped object accelerates and calculate
the acceleration due to gravity.
2) Explain how the mass of an object affects its acceleration due to gravity.
3) Explain how the distance by a dropped object covers changes as time goes by.
Procedure:
Objective 1
Set up your ticker tape as Mr. Kibala did. Drop the ticker tape through the timer
with a 20 g mass attached to the ticker tape.
Each lab partner will choose two adjacent pairs of dots, calculate the velocity for
each pair of dots, decide what period of time separates each pair of dots, then
calculate the acceleration of the mass due to gravity using the two velocities. Do this
in the space below. Each lab partner should choose their own pair of adjacent
velocities to calculate acceleration. Put your velocity next to your name in the
google doc.
v=d/t
a=change in v /t
What is the class average for the acceleration of the 20 g mass due to gravity: ________
Next draw a strobe photo of the dropped object below.
Velocity vs Time Graph:
Next fill in the table below by finding the velocity for each pair of dots represented
by the beginning and ending time in each time interval in the table. Use v=d/t.
You may have calculated some of these already
Velocity (m/s)
Time Interval (s)
Midpoint in time interval (s)
0-.025
.0125 s
.025-.05
.05 - .075
.075-.1
.1-.125
.125-.15
.15-.175
.175-.2
.2-.225
.225-.25
Graph: Using Excel Graph the Midpoint in the time interval on the x-axis and the
Velocity on the y-axis. Label each axis with, x-axis as time and y-axis as velocity.
Include the units in the axes labels as well. Move the graph to its own sheet and
choose a Linear fit for the graph and get the slope for your linear fit from Excel.
Questions:
1) What does the slope of a Velocity vs Time graph represent?
2) What is the acceleration of the due to gravity using this analysis method?
Distance vs Time Graph:
Next fill in the table below using your ticker tape and a meter stick or ruler to
measure the ticker tape. This table will be used to make a distance versus time
graph.
Distance (m)
Time (m)
Graph: Using Excel Graph the Time on the x-axis and the Distance on the y-axis.
Label each axis with, x-axis as time and y-axis as distance. Include the units in the
axes labels as well. Move the graph to its own sheet and choose an Exponential fit
for the graph.
Questions:
1) Using each the distance vs time graph and the velocity vs time graph as evidence
explain below how you can support the claim that the dropped object accelerates.
Objective 2
Previously you dropped the ticker tape through the timer with a 20 g mass attached
to the ticker tape. You chose two pairs of dots that were adjacent. You calculated
the velocity for each pair of dots, decided what period of time separates each pair of
dots, then calculated the acceleration of the mass due to gravity. You will be
assigned a new mass, which you will list below and drop that mass through the
ticker tape, then use the same method as you used for the 20 g mass to find the
acceleration of the new mass. In the table below you will list the average
acceleration the class calculated for the 20 g mass in objective1, the acceleration of
the other mass you are assigned and the rest of the class’s accelerations listed in the
google doc.
Mass ____________
Calculation of acceleration using ticker tape:
Acceleration
Class average:
Mass
20 g
40 g
100 g
120 g
140 g
150 g
Next calculate the acceleration for all of the masses dropped by the class using F =
ma. The Force is the dropped objects weight. The acceleration you calculate in this
section is the theoretical acceleration we should achieve.
20 g:
_________________________________________________________________________________________________
40 g:
_________________________________________________________________________________________________
100 g:
_________________________________________________________________________________________________
120 g:
_________________________________________________________________________________________________
140 g:
150 g:
_________________________________________________________________________________________________
Questions:
1) Why is the theoretical acceleration you should achieve always the same
every time you calculate it?
2) How does calculating the theoretical acceleration using F=ma show that mass
does not affect the acceleration of an object due to gravity? Show that mass
does not affect acceleration due to gravity mathematically. Hint: where do
the m’s cancel?
3) What other outside Force, besides weight, may have affected your
experimental measurements using the ticker tape so you did not achieve the
theoretical acceleration due to gravity using F=ma?
4) In the 1500’s the dominant thought was an object that is 5 times heavier will
reach the ground 5 times as fast or an object that is 10 times heavier will
reach the ground 10 times faster. Galileo proposed during this time that if air
was removed all objects would fall at the same rate, therefore hitting the
ground at the same time. Using this experiment you performed, explain if
you agree with Galileo and your reasons why.
Objective 3
Use the distance & time table and graph you created in objective 1 for this objective
3.
1) When the time of flight doubles by what factor does distance increase?
2) When the time of flight triples by what factor does distance increase?
3) When the time of flight quadrupels by what factor does distance increase?
4) Multiply half your acceleration due to gravity, also known as g or 9.8, by any
of the times in the table squared (d=1/2gt2). Do this for 3 different times. Do
you get the distance from the distance column in the table that is across from
each of these times?