Consider a body projected from a point O on the surface of the Earth with an initial velocity u at an angle 8 with the horizontal as shown in Figure. The velocity u can be resolved into two components.
Fig: Motion of a projectile projected at an angle with the horizontal
(i) ux = it cos θ, along the horizontal direction OX and
(ii) uy = u sin θ, along the vertical direction OY
The horizontal velocity ux of the object shall remain constant as no acceleration is acting in the horizontal direction. But the vertical component uy of the object continuously decreases due to the effect of the gravity and it becomes zero when the body is at the highest point of its path. After this, the vertical component uy, is directed downwards and increases with time till the body strikes the ground at B.