Engineering Mechanics
The total momentum of a system of masses (i. e. moving bodies) in any one direction remains constant, unless acted upon by an external force in that direction. This statement is called

Principle of conservation of momentum
Newton's second law of motion
Principle of conservation of energy
Newton's first law of motion

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Engineering Mechanics
The Cartesian equation of trajectory is (where u = Velocity of projection, α = Angle of projection, and x, y = Co-ordinates of any point on the trajectory after t seconds.)

y = x. tanα - (gx²/2u² cos²α)
y = x. tanα + (gx²/2u² cos²α)
y = (gx²/2u² cos²α) + x. tanα
y = (gx²/2u² cos²α) - x. tanα

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