Name ________________________ Period _____
Lab: Determining the Range of a Horizontal Projectile
Purpose: To find out if the motion equations really work for determining projectile range.
Procedure: We will be comparing the actual range that we measure for a ball that is launched off a ramp
horizontally to the range that we calculate for that ball using motion equations.
To perform the experiment:
 Clamp the launch ramp to the very edge of the table.
 Measure and record the distance “D” from the overhang edge of the ramp to the floor
 Tape your data sheet of paper (approximately 50 cm x 100 cm) with the carbon paper
placed face down over it to the floor with approximately 10 cm of paper under the
table, and the rest extending out from the table edge along the flight path as shown.
 Use a plumb line (paper clip tied to thread) held at the end of the ramp to mark the
paper directly beneath the launch point at the end of the ramp with a dot. This is your
starting point for the actual range distance. Label the dot with “Start”
 Start the ball at the top of the ramp and measure the vertical distance from the ramp
top to the table top. Record this distance in the “H” column of your data table.
 Measure the length “L” along the table from beneath the release point on the ramp to
the launch point.
 Calculate and record the angle  of the ramp using tangent of  = H/L
 Release the ball from the very top of the ramp, and after it hits the floor, lift up the
carbon paper and write “trial #1” next to the carbon dot mark on the paper.
 Cross out any marks left by ball bounces.
 Measure and record the range of the ball on your data sheet and in your data table
 Repeat the last six steps four more times, starting the ball at a different place on
the ramp above the table each time. Record each new ramp height above the table
and label each new paper mark with its trial number immediately after the ball hits.
 Calculate the launch velocity vox of the ball coming off the ramp for each trial using
the motion equation: vf2 = 2g(sin)H. ( vf in this equation will actually be the
starting velocity vox for the projectile part of the motion.)
 Calculate the time t for the projectile motion using D = ½ at2 . D is the distance
from the table top to the floor.
 Calculate the range dx for each trial using the motion equation dx = vot
 Compare your calculated values for dx to the ones you actually measured using a
percent difference calculation with the measured range as the actual value.
ball
ramp
H
vox
L
Plumb line
Carbon paper
Data sheet
Data Table:
Trial
Distance from table top to floor: D (cm) ________
H (m)
Ramp
top to
table top
L(m)
Along table
Top beneath
ramp
Sample Calculations:
Quantity calculated
dx (m)

measured
range
Tan-1
(H/L)
vox (m/s)
g(sin
cm/100 = m
for ramp
tan-1 (H/L)
a for ramp
a=g sin 
Launch vox (m/s)
(vf coming off table)
t (s)
vf2 = 2aH
dx (m)
(calculated range)
% Difference
of ranges
(vf for ramp is
vox for launch)
Formula Used
cm to meters
(for fall to ground)
D (m)________
t (s)
for fall
to ground
dx (m)
calculated
range
Substitution using
your data
% Difference
of ranges
Answer with
Units
D = ½ gt2
dx = voxt
(vf ramp = vox launch)
% Diff = ( meas. dx – calc. dx) (100)
( meas. dx)
Questions:
1. Overall, how did your actual ranges (measured dx values) compare to your calculated ranges?
(smaller, larger, not anything like, the same)
2. What are three different factors that might have caused the differences between your measure range
value and your calculated range value?
a.
b.
c.
3. Explain specifically (according to your average results using a demonstration calculation and diagrams
if necessary) how each factor you mentioned above in answer to question #2 would have affected your
percent difference. For example, if you mis-measured a value, estimate by how much you would have
mis-measured it and show how your calculation of the quantity and the resulting percent difference
based on that measurement would be affected.
Factor a:
Factor b:
Factor c:
4. Do you believe that the motion equations work for giving realistic values for projectile ranges?
Justify your answer.