Consider it being thrown with an angle θ with the horizontal.
Then the velocity has two components ux=Ucosθ and uy=Usinθ.
The horizontal acceleration is ax=0 while that in vertical direction is ay=−g
From an equation from kinematics,
y=uyt+12ayt2
⇒y=Usinθt−12gt2 is distance travelled by particle in y direction (vertical direction) in time t.
Also, x=uxt+12axt2
⇒x=Ucosθt
Combining x and y,
y=xtanθ−12gx2cos2θ
But for θ constant, tanθ=a and b=−g2cos2θ,
We get,
y=ax+bx2
Which shows that the path is parabolic.
The equations of motion are,
Fx=max=0
Fy=may=−mg
If however, the body is thrown vertically up, θ=π2
And thats when the x component of motion ceases the exist and, motion can be described as, by acceleration ay=−g.
Then, y=Ut−12gt2 describes the vertical distance travelled.