Project 1: Snowball Attack
Suppose it's a cold, snowy day when you're walking along Pollock Road and notice your computer science
instructor standing outside the IST Building entrance talking to one of your classmates. You decide to try to
hit him with a snowball. (Because you're a good student, you'd
never
do this.
.. right?) Will you succeed?
Now that you've learned several of the basic concepts of C++ programming, you can write a program that
puts many of your skills to use together to predict whether or not your snowball attack will be a success.
You'll have an opportunity to create a longer program where the process consists of several steps instead of
just one or two and learn some important things about the flow of a program from this experience.
First, let's take a moment and recall some basics of kinematics from our intro. physics experience. When you
throw the snowball, it becomes a projectile and will be governed by the laws of kinematics. The snowball is
thrown with some velocity, which is a vector quantity. That means it has both a magnitude and direction.
We'll express the direction as an angle with respect to the horizontal. When we do computations, we need to
resolve the vector quantities into components and work with the
x
direction separately from the
y
direction.
Recall that we resolve a vector
v
at direction θ into its horizontal and vertical components using
trigonometry:
•
v
x
=
v
(cos θ)
•
v
y
=
v
(sin θ)
We can then use the equations of kinematics:
1.
v
f
= v
i
+ at
2.
v
f
2
=
v
i
2
+ 2
ad
3.
d
=
v
i
t
+ (1/2)
at
2
where
•
v
f
= final velocity
•
v
i
= initial velocity
•
a
= acceleration
•
t
= time
•
d
= distance
In the vertical direction, the acceleration we use is the constant acceleration due to gravity,
g
= 9.8 m/s
2
or
g
= 32 ft/s
2
. In the horizontal direction, the projectile does not experience any acceleration (which simplifies
Equation #3 above for our computations).
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 Fall '10
 Acceleration, Velocity, snowball, snowball attack

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