# ^What is a projectile

^What is a projectile

A projectiles is any object moving under the influence of gravity.  There are several ways to throw a projectile, vertically up, vertically down, horizontally, at some angle up, at some angle down etc.

1. Object is thrown means initial speed non zero.
2. Object is dropped means initial speed zero.Assumptions

Following are few assumptions in the study of projectiles.

1. Projection speed u << v escape so that g remains constant with the height & equations of UAM can be used to study the problems based on projectiles.
2. Wind is absent for simplicity of mathematics.
3. Air friction is absent if not specified so that the mechanical energy of the projectile remain constant throughout the motion. i.e.

K + U = same at all the points of trajectory.

4. The acceleration of any projectile on earth is a = constant = g = 9.8 m/s2 = 32 ft/s2 directed towards the centre of the earth irrespective of its mass, position, time, speed of projection & angle of projection. As the acceleration of a projectile is ‘g’ acting along – y, thus it has no x & z components.

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