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## projectile

In the absence of air resistance there are no forces or components of forces that act horizontally. A velocity vector can only change if there is acceleration acceleration is the rate of change of velocity. In the absence of air resistance the only force acting on a projectile in flight is the weight of the object. Weight by definition acts vertically downwards, hence no horizontal component. Gravity opposes the vertical component of velocity of the projectile with which it has been projected. Now suppose a projectile is projected with an initial velocity u at an angle theta w. So,vertical component of its velocity is u sin theta ,so the projectile will keep on moving up,untill it's upward velocity becomes zero due to the downward direction of gravitational force acting on it. So, at the highest point of its motion,the projectile has no vertical component of velocity,only horizontal component of velocity exists. After that the projectile starts coming down being accelerated by gravity. So it's height decreases and at a time it reaches the ground. So where,the horizontal component of velocity pushes it forwards,vertical component of velocity pushes it upwards,but it comes back to the ground just because of the gravitational force. Actually whilst the ball is in contact with the foot it is not a projectile. A kicked football is an example of a projectile i. A projectile is an object that moves under the influence of gravity, what that means is that it's weight is the only force that acts upon it. In reality there is a drag force too, but that is frequently ignored for the purpose of projectile calculations. Whilst being kicked the ball has a normal reaction force from the foot acting upon it in addition to its weight. So that does not count as a projectile. After being kicked the ball only has its weight and drag acting upon it, so it is a projectile. Whilst in flight the ball will continue with constant horizontal velocity no horizontal forces and experience a constant downwards vertical acceleration due to its weight. Projectile motion is parabolic because the vertical position of the object is influenced only by a constant acceleration, if constant drag etc. However, I can explain a bit more in-depth why this works, if you'd like, by doing a little integration.

## Projectile Motion Projectile motion is the motion of an object thrown or projected into the air, subject to only the acceleration of gravity. The object is called a projectileand its path is called its trajectory. The motion of falling objects, as covered in Problem-Solving Basics for One-Dimensional Kinematics, is a simple one-dimensional type of projectile motion in which there is no horizontal movement. The most important fact to remember here is that motions along perpendicular axes are independent and thus can be analyzed separately. This fact was discussed in Kinematics in Two Dimensions: An Introductionwhere vertical and horizontal motions were seen to be independent. The key to analyzing two-dimensional projectile motion is to break it into two motions, one along the horizontal axis and the other along the vertical. This choice of axes is the most sensible, because acceleration due to gravity is vertical—thus, there will be no acceleration along the horizontal axis when air resistance is negligible. As is customary, we call the horizontal axis the x -axis and the vertical axis the y -axis. The magnitudes of these vectors are sxand y. Note that in the last section we used the notation A to represent a vector with components A x and A y. If we continued this format, we would call displacement s with components s x and s y. However, to simplify the notation, we will simply represent the component vectors as x and y. Of course, to describe motion we must deal with velocity and acceleration, as well as with displacement. We must find their components along the x — and y -axes, too. We will assume all forces except gravity such as air resistance and friction, for example are negligible. Note that this definition assumes that the upwards direction is defined as the positive direction. If you arrange the coordinate system instead such that the downwards direction is positive, then acceleration due to gravity takes a positive value. Both accelerations are constant, so the kinematic equations can be used. Figure 1. The total displacement s of a soccer ball at a point along its path. The vector s has components x and y along the horizontal and vertical axes. Step 1. Resolve or break the motion into horizontal and vertical components along the x- and y-axes. The magnitude of the components of displacement s along these axes are x and y. Initial values are denoted with a subscript 0, as usual. Step 2. Treat the motion as two independent one-dimensional motions, one horizontal and the other vertical. The kinematic equations for horizontal and vertical motion take the following forms:. Step 3. Solve for the unknowns in the two separate motions—one horizontal and one vertical. Note that the only common variable between the motions is time t.

## What is Projectile Motion? Learn something new every day More Info Projectile motion is a physical phenomenon that occurs when an object is projected by a force that stops exerting influence on the object after it has been launched. The laws of physics cause objects to follow a very particular path when they are launched in this way. A classic example is a soccer ball, which becomes a projectile when it is kicked by a player. Most people are familiar with Isaac Newton's statement that an object in motion tends to remain in motion. This is known as inertia. Inertia plays an important role in projectile motion, because it explains why an object keeps moving without any source of propulsion. There is also a force at play: gravity. Gravity explains why the soccer ball in the above example returns to Earth, rather than moving continuously through the air. The path of a projectile is roughly parabolic. When it is launched, the inertia helps it move upwards, against gravity, but eventually gravity's pull becomes too strong, and the object starts to loop back to Earth. The object has also been traveling horizontally, however, so the path of the object creates an arc. Eventually, the object will hit the Earth and come to rest, and in the case of the soccer ball, to be kicked by another player. Understanding how projectile motion works is important. Historically, many armies struggled with the concept, because they didn't understand how arrows, cannonballs, bullets, and other projectiles moved through the air, and this made it difficult to aim properly. The physics behind this type of motion also plays a role in sports and many other activities, which is why questions involving this concept ask people to use mathematical formulas to determine the path that a projectile will follow occur on so many physics tests. The initial velocity of the object, mass, and angle of launch all play a role in the path that the object will follow; for example, a marble that rolls off a table will follow a different route than one that is launched upwards with a small catapult. Most projectile motion problems are set on Earth, which has a familiar gravity, although people can also calculate it for various objects on other planets, as long as the gravity is known. Simple problems also assume that air resistance and the Earth's rotation are unimportant, although in fact they can become issues with certain types of problems. The curved vertical motion of a body is called projectile motion. This motion is under the force of gravity and is of two dimensional.

## Projectile motion 