Projectile MotionNotes and Practice

Vocabulary

• Projectile• Trajectory• Gravity• Acceleration due to gravity (g)• Terminal Velocity• Horizontal Component• Vertical Component• Air resistance

Projectile:

• A projectile is a particle moving near the Earth’s surface under the influence of gravity only (directed downward).

Vertical Motion

• Objects in free fall are affected by acceleration due to gravity, a rate of 9.8 m/s/s on earth.

• Velocity downward will ____________ until the projectile has reached its _________ velocity.

• Since there is an acceleration component to vertical motion, we must use FIAT to determine velocity (final = initial + at).

Horizontal Motion

• Once a projectile is released, there is no force acting on it aside from its weight, which depends on gravity. Therefore, there is never any horizontal acceleration in the absence of air resistance.

• This means that the horizontal component of a projectile’s velocity does not change from its horizontal velocity at launch.

Displacement Calculations For General Projection:

The components of displacement at time t are:

212ox xx v t a t

For projectiles:

0; ; 0; x y oy ox oa a g v v v

212oy yy v t a t

Thus, the displacement components x and y for projectiles are:

212

ox

oy

x v t

y v t gt

Example 1: A baseball is hit with a horizontal speed of 25 m/s. What is its position and velocity after 2 s?

25 m/s

xy

First, find the horizontal and vertical displacements. Then, find the velocity components after 2 s.