For any projectile launched horizontally, the projectile is given an **initial** horizontal velocity. The cannonball will also accelerate horizontally due to free fall. The goal of this lesson is to show you the trajectory of the cannonball.

The initial vertical velocity is of course equal to 0.

For, example, let's say that you launch a cannonball horizontally as shown in the picture below.

Once the cannonball is in the air, there are two things happening with the cannonball at the same time.

The cannonball will be affected by the horizontal speed and the vertical speed.

First, let us talk about the horizontal speed. Notice that there is no horizontal acceleration because there is no
horizontal force acting on the cannonball . With no horizontal
acceleration, the cannonball will move horizontally with constant
velocity.

Below, we show constant velocity for the cannonball by using vectors that have the same size.

Second, as the cannonball move horizontally, gravity will force the cannonball to fall vertically as well. Therefore, the cannonball will experience free fall. We saw in the lesson about free fall that objects in free fall accelerate.

This means that the speed is not
constant, but keep on increasing. Since the speed is increasing, the
object will cover a greater distance in each successive equal time
interval. Below, we show a speed that is increasing as the cannonball experiences free fall.

We can combine the vertical and horizontal movement/speed of the
cannonball to see what we end up with. See below the horizontal speed,
the vertical speed, and the resultant speed in red. The ball move along
the green curve which is a parabola. The vectors shown in red (resultant
speeds) are tangent to the green curve although it does not look
perfect.

The path traced above in green is the path that a projectile will follow when the following conditions are met.

- The projectile is accelerating only in the vertical position only.

- Air resistance is negligible or not important. Air resistance is not important when the object is very heavy or the object is moving slowly.

Next, we learn about the path and speed of a projectile launched at an angle.

This projectile launched horizontally quiz will help you see how the
velocity and acceleration behave when the projectile is launched
horizontally. You will not need to use a paper and pencil to complete
this quiz.

First, read the lesson about projectile launched horizontally and then take this quiz.

Objective of the quiz:

- recognize the path of projectiles launched horizontally.
- See how the horizontal velocity and the horizontal acceleration behave.
- See how the vertical velocity and the vertical acceleration behaves.
- Understand when air resistance is negligible.