Name ___________________________________ Date ___________________________________
Projectile Motion Simulation
Forces & Gravity CD-ROM
Activity 2
Introduction
Will a feather and a baseball hit the ground at the same time? What we know about gravitational force tells us that
they should. Galileo’s famous experiments dropping objects off the tower in Pisa proved that weight doesn’t matter
in how fast an object falls. However, this is only true for free fall. Free fall is when there is no air resistance. Earth
does have air resistance. The feather will float to the ground slowly because of air resistance. Its easy to image air
resistance on a feather or a piece of paper, but air resistance is a force that affects all objects.
A softball and a baseball will both experience the same air resistance, even though they have different masses and
different diameters. Near the surface of the Earth, it’s hard to encounter a distance large enough for air resistance to
act differently on these two balls when dropped straight down.
When pitched, a baseball does not just move downward. The movement is in two directions--horizontally and
vertically. Does the air resistance on these two vectors, or directions, combine to make a difference in the distance
baseballs of different masses travel?
Directions
Use the Projectile Motion simulation to test how air resistance and mass interact to affect the distance you can
throw a baseball.
Procedures
Part 1
1. From the Main Screen select the Simulations icon. Then click the Projectile Motion icon.
2. Click on the Start Here button and read the text. If you need more information, click and read the
Background. Close the window when you are done.
3. On the top right of the screen is a list of variables. From the pull down menu under Ball’s Mass, select Normal
Baseball. Under Speed, select 20 m/s. You will keep these variables constant in Part 1.
4. From the pull down menu under Pitch Angle, select 15 degrees. From the pull down menu under Location,
select Earth with No Air Resistance.
5. Click on the Pitch Ball button in the lower right hand corner. Observe the path of the ball. In the table below,
record the distance, height, and hang time of the pitch.
Earth with No Air Resistance
Pitch
Angle
Distance
(m)
Height
(m)
Hang
time (s)
Earth with Air Resistance
Distance
(m)
Height
(m)
Hang
time (s)
15°
30°
45°
60°
75°
6.
7.
8.
Keeping Ball’s Mass, Speed, and Location constant, repeat this trial for all the angles under Pitch Angle.
Observe the path and record the results in the table.
Click on the Reset button. Under Location, select Earth with Air Resistance. Repeat the steps above,
recording your results in the table above.
What can you conclude about the effect air resistance has on the distance a pitched baseball will travel? Does
the angle of the pitch seem to make any difference?
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Name ___________________________________ Date ___________________________________
Procedures (continued)
Part 2
The pitcher’s arm is like a lever or catapult. The pitcher’s body provides force, as does the leverage action of his
arm. The formula a = F/m is used to determine the effect of mass on the acceleration that an object experiences
from the force applied to make it move. What this means is that if the same amount of force is applied to two
objects, the object with the larger mass will experience a smaller amount of acceleration. Another way to think
about this is that in order to get the same speed, the pitcher will have to apply more force to a heavier baseball.
9. Click on the Reset button. From the pull-down menu under Ball’s Mass, select Normal Baseball. Under
Speed, select 40 m/s. From the pull down menu under Location, select Earth with Air Resistance.
10. From the pull down menu under Pitch Angle, select 15 degrees. Click on the Pitch Ball button in the lower
right hand corner. Record the distance, height, and hang time in the table below.
Normal baseball
Pitch
Angle
Distance
(m)
Height
(m)
Hang
time (s)
Heavy Baseball
Distance
Height
(m)
(m)
Hang
time (s)
15°
30°
45°
60°
75°
11. Repeat steps 9 and 10 for a Heavy baseball. Record those results in the table.
12. Use your calculator to find the ratio of the distance traveled by the heavy ball to the distance traveled by a
regular ball. Then find similar ratios using maximum height and hang time.
Ratio of heavy ball / normal ball
Angle
15°
30°
45°
60°
75°
Distance
Height
Hang time
13. What patterns do you find in the ratios? Think about the affect of pitch angle and air resistance as you look at
the ratios for distance, height, and hang time.
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14. If you threw a regular ball 35 meters, how far would you expect the heavier ball to go with a similar throw?
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15. Speed is not the same as acceleration, but in this simulation the result is about the same. In physics, you find the
force required to achieve a desired acceleration by multiplying mass and acceleration: f=ma. Find the force at
which a regular and two heavier balls would have to be thrown to travel at a speed of 40m/s. The unit for force
is a Newton, which is equal to kg * m/s. Do you think that you could throw each ball with that much force?
Mass of ball
Regular ball (0.15)
Heavy ball (0.30)
1-kg ball
Force at 40 m/s
16. Look at your data again for the distance that each pitch traveled. If you could throw the 1-kg ball with the
necessary force for it to travel at 40m/s at a 45° angle, how far would it travel? What would be the hang time?
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