Can an object dropped from a moving plane achieve purely vertical motion?

[Gaboon]

Hi all,
I have a very simple question. Will an object dropped from a plane moving at a constant velocity ever achieve purely vertical motion? (Make sure we're not taking air resistance into account)
Thanks

 

[berkeman]

Hi all,
I have a very simple question. Will an object dropped from a plane moving at a constant velocity ever achieve purely vertical motion? (Make sure we're not taking air resistance into account)
Thanks

No. If there is no air resistance, the horizontal velocity of the object stays fixed at the velocity of the plane.

 

[Gaboon]

How about direction?

 

[berkeman]

How about direction?

I don't understand the question. The object follows a projectile trajectory. Are you familiar with the equations of projectile motion with constant acceleration (gravity) and with the simplifying assumption of no air resistance?

 

[Gaboon]

Yes. Does that trajectory ever lead to object falling at 90 degrees to earth?

 

[berkeman]

Yes. Does that trajectory ever lead to object falling at 90 degrees to earth?

No, it can't. The horizontal velocity never decreases, so the object will never fall vertically. The vertical speed keeps increasing when there is no air resistance, so the vertical angle gets smaller and smaller, but it never goes to zero.

 

[ZapperZ]

Yes. Does that trajectory ever lead to object falling at 90 degrees to earth?

Only if you fall along with the object.

Zz.

 

[Gaboon]

Ok thanks for feedback. Though I would love to know why the vertical angle never reaches zero.

 

[ZapperZ]

Ok thanks for feedback. Though I would love to know why the vertical angle never reaches zero.

Read Berkeman's reply in Post #2! I have a feeling that the significance of that explanation escapes you somehow.

Zz.

 

[russ_watters]

Ok thanks for feedback. Though I would love to know why the vertical angle never reaches zero.

You'll recognize that if there is always horizontal motion, the angle can't be zero, right? Or are you unclear about why the horizontal speed is fixed? That's due to Newton's first Law.