Projectile motion conceptual question

[madah12]

Homework Statement

if an object is thrown vertically downwards from an airplane moving horizontally with constant velocity would the object fall in a straight line or in a parabolic path

Homework Equations

The Attempt at a Solution

I know it is supposed to fall in a parabolic path because of Newtons first law and it should have the horizontal velocity of the airplane but when I do it with projectile equations
when measured from the horizon theta = 90

vx1=vcos90 = v*0=0
vy1=vcos0 =v
ax1=0
ay1=g
so there is no acceleration or velocity in x so it is supposed to be free fall
so why does the formula for the projectile motion contradict what happens truly?

 

[Doc Al]

when measured from the horizon theta = 90

The initial velocity is horizontal, so the angle would be 0 not 90.

 

[madah12]

oh I see then vx1=vcos0=v
and vy1=vcos90=0
it makes sense now
thanks

 

[mugaliens]

The initial velocity is horizontal, so the angle would be 0 not 90.

Is it? The problem statement said it was "thrown vertically downwards," so the angle would be negative.

Regardless, all objects fall in parabolas (simiplified flat-Earth solution from the elliptical), regardless of initial vectors/velocities.

 

[Doc Al]

Is it? The problem statement said it was "thrown vertically downwards," so the angle would be negative.

Good point! I misread that as 'dropped vertically downwards' with respect to the plane.

Nonetheless, the key point is that there is an initial horizontal velocity component due to the motion of the plane.