Presentation on theme: " Any object that moves through the air or through space, acted on only by gravity A projectile is any object which once projected continues in motion."— Presentation transcript:
Any object that moves through the air or through space, acted on only by gravity A projectile is any object which once projected continues in motion by its own inertia and is influenced only by the downward force of gravity. inertia Examples – a stone thrown into the air, a ball rolling off a cliff, a cannonball shot from a cannon.
1.Horizontal Component of Motion – similar to a ball rolling freely along a level surface; when friction is negligible, a rolling ball will move at a constant velocity (equal intervals of time). 2.If there is no horizontal force acting on the object, there is no horizontal acceleration.
2. Vertical Component of Motion – similar to a freely falling object – acceleration due to ____________???. As the ball falls, the increasing speed causes a greater distance to be covered each second.
**The ball follows a “parabolic” path.**
The horizontal and vertical velocity components of vectors are independent of each other (have no affect). But… the combined effects of each component produce the curved paths that projectiles follow. What do you call the sum or product of two projectile vectors?
Suppose the zookeeper must shoot the banana from the banana cannon to the monkey who hangs from the limb of a tree. This particular monkey has a habit of dropping from the tree the moment that the banana leaves the muzzle of the cannon. The zookeeper is faced with the dilemma of where to aim the banana cannon in order to hit the monkey. If the monkey lets go of the tree the moment that the banana is fired, then where should she aim the banana cannon? To ponder this question, first consider a scenario in which there is no gravity acting on either the banana or the monkey. What would be the path of the banana? Would the banana hit the monkey?
If the monkey lets go of the tree the moment that the banana is fired, then where should she aim the banana cannon? To ponder this question, consider the scenario in which the zookeeper aims above the monkey (perhaps she presumes that gravity will accelerate the banana downward such that it hits the monkey). What would be the path of the banana? Would the banana hit the monkey?
To ponder this question, consider the scenario in which the zookeeper aims at the monkey and shoots the banana very fast (perhaps she presumes that if shot fast enough, the banana will hit the monkey before it falls very far). What would be the path of the banana? Would the banana hit the monkey?
If the monkey lets go of the tree the moment that the banana is fired, then where should she aim the banana cannon? To ponder this question, consider the scenario in which the zookeeper aims at the monkey, yet shoots the banana very slow. What would be the path of the banana? Would the banana hit the monkey?
A projectile is an object upon which the only force is gravity. Gravity acts to influence the vertical motion of the projectile, thus causing a vertical acceleration. The horizontal motion of the projectile is the result of the tendency of any object in motion to remain in motion at constant velocity. Due to the absence of horizontal forces, a projectile remains in motion with a constant horizontal velocity; horizontal forces are not required to keep a projectile moving horizontally. The only force acting upon a projectile is gravity!
Imagine a pickup truck moving with a constant speed along a city street. In the course of its motion, a ball is projected straight upwards by a launcher located in the bed of the truck. What will be the path of the ball and where will it be located with respect to the pickup truck?
1. As can be seen from the above animation, the ball follows a parabolic path and remains directly above the launcher at all times. 2. As the ball rises towards its peak, it undergoes a downward acceleration. a) An upwardly moving ball which is slowing down is said to be undergoing a downward acceleration. 3. As the ball falls, it also undergoes a downward acceleration. a) A downwardly moving ball which is gaining speed is said to have a downward acceleration. b) This downward acceleration is attributed to the downward force of gravity which acts upon the ball. 4. If the ball's motion can be approximated as projectile motion (that is, if the influence of air resistance can be assumed negligible), then there will be no horizontal acceleration. 5. In the absence of horizontal forces, there would be a constant velocity in the horizontal direction. 6. This explains why the ball would be located directly above the launcher from which it is projected. 7. Many would insist that there is a horizontal force acting upon the ball since it has a horizontal motion. a) This is simply not the case. b) The horizontal motion of the ball is the result of its own inertia. c) When projected from the truck, the ball already possessed a horizontal motion, and therefore will maintain this state of horizontal motion unless acted upon by a horizontal force.
12. A plane is flying at an altitude of 8000 m at a sped of 250 m/s. At what horizontal distance ahead of its target must a water balloon be released to strike the target on the ground(neglecting air resistance)?