Projectiles

Introduction: Projectile definition

Projectile motion is the movement of an object launched or projected into the air and is only affected by gravity’s acceleration. The object is the projectile, and the path it follows is its trajectory. 

The falling object motion is a one-dimensional projectile motion and doesn’t involve any horizontal movement. This section will look at two-dimensional projectile motion, such as that of a football or other low-air-resistance object.

A projectile meaning states that only one force, gravity, acts on the projectile. If any other force were acting on an object, it would not be considered a projectile. As a result, a projectile’s free-body diagram would display a single downward-acting force labelled force of gravity (or simply Fgrav). 

The free-body diagram remains the same whether it is going anyway. A projectile, by definition, is thus any item whose only force is gravity.

What is motion in a plane?

When a projectile is thrown awkwardly near the earth’s surface, it moves simultaneously horizontally and vertically. Projectile motion is the name given to the motion of such a particle. 

Assume that we project a particle with an initial velocity of u at an angle of θ. In this example, we will do the following calculations:

• The time it takes to get from point O to point A
• The distance travelled horizontally (OA)
• At any point “t” during the motion, the velocity “v”

Projectile examples

In addition to the projectile definition, it is essential to have an understanding of the projectile examples:

• A baseball that has been batted, tossed, or pitched
• A bullet as it emerges from a gun or rifle’s barrel
• A bus that has been driven off an unfinished bridge
• A moving plane in the air with crippled engines and wings
• A runner in the middle of a stride (since they momentarily lose contact with the ground)
• When the main engine of the space shuttle or any other spacecraft has been turned off. This phenomenon is called MECO.

Projectile motion and inertia

Many pupils struggle to understand that gravity is the only force acting on an upward travelling projectile.

Their understanding of motion leads them to believe that if an object is travelling upward, it must be under the influence of an upward force. And if an object is travelling upward and rightward, both upward and rightward forces must be present.

They believe that forces cause motion and that there must be an upward force if there is upward motion. After all, how can an object be travelling upward if the only force acting on it is gravity? 

That is where Newtonian physics comes into play.

Remember how Newton’s principles contradicted the widespread belief that a force must propel an item to remain in motion. That is not the case! 

It is not necessary to apply force to keep an object moving. A force is simply needed to maintain acceleration. In the case of an upward-moving projectile, there is also a downward force and a downward acceleration. That is to say; the item is ascending and slowing down.

Important Points of Projectile Motion

• A projectile’s course is parabolic.
• The kinetic energy is (1/2) mv2 at the lowest position. Where v is the velocity.
• The linear momentum is equal to mv at the lowest position.
• The projectile’s acceleration is persistent during the motion and operates vertically downwards, equal to g.

Conclusion

A projectile is an item on which gravity is the only force acting. Gravity influences the projectile’s vertical motion, resulting in vertical acceleration. 

The tendency for any moving object to maintain a constant velocity is responsible for the projectile’s definition of horizontal motion. A bullet maintains a steady horizontal velocity due to the lack of horizontal forces. No horizontal forces are required to keep a bullet moving horizontally.