Ignoring Air resistance, the horizontal velocity of a thrown object never changes. True or False?

Question

This question was on a science test I took at school. I think its false because gravity will eventually make the object fall to the ground, but my teacher won´t listen to me.
What do you think?---------------

"Ignoring air resistance, the horizontal velocity of an object never changes". True or False.----------

Answer 1

Silly... The point your instructor is making is that barring any impeding object (air) in the horizontal(to the ground) velocity vector will remain the same (First Law of Motion). Of course his use of never is inappropriate. Any thrown object will eventually fall, go into orbit, or escape earth's gravity and fly into space. At which point the object might encounter another impeding object...
I recommend that you suggest to your instructor that he reword the question. (Forget trying to get the point). Explain to him that Newton's First Law states "An object at rest tends to stay in rest and an object in motion tends to stay in motion in a straight line at constant speed unless acted upon by an outside force."... Notice Newton himself refrains from the use of NEVER and uses the unless clause. Explain to the instructor that you were using the UNLESS in the 1st Law. That is to say he did not tell you to ignore gravity or any other impeding objects. So, tell the instructor that you now understand what he was asking BUT s/he would be better off either taking out the NEVER (which Newton would not have used) with "until it hits the ground."

Addition:
Given the Q as a true/false statement and understnading that the question is asking about Newton's First Law and knowing that even Newton says "nisi quatenus a viribus impressis cogitur statum illum mutare." which means "unless acted upon by an external and unbalanced force." I would say FALSE!
(The word "never" should not have been used).

Answer 2

True, if you ignore all resistance and have an object with a horizontal velocity, this will never change. At this point keep in mind that you are only considering one direction, that you call horizontal because that is commonly known as "parallel to the ground" and of course is not true because the ground is not a straight line, but follows the curvature of the earth and is therefore a segment of a circle. When you bring in the gravity force, you have introduced a second component to the object thrown, this second component would be the gravity force which attracts the object towards the center of the earth and that if you are true to the same initial conditions on the object, there would also not be any resistance, therefore the velocity would not be constant and the object would continously accelerate in that "downward" direction until it would hit the ground. Make your analysis a little more extreme and you have a satellite. Imagine you are Superman and have flown so high that gravity can still be felt but there is no longer air resistance, or at least it is so small it can be disregarded. At that point you throw the object horizontally, the object does not follow a straight line because there is the vertical component caused by gravity pulling upon the object toward the center of the earth therefore the object loses a certain amount of vertical distance as it goes hurling along the horizontal throw. If the initial velocity that Superman gave the object is not very great, then the object will make a spyral trajectory losing more and more vertical distance until it crashed to earth. If the initial velocity given by Superman is truly great, the object will have travelled so far in the initial horizontal direction and so little in the vertical distance lost that the object will soon be so far away that earth's gravitational field will no longer affect it, then the object will continue going forever in space. Finally, if the initial velocity given by Superman is just right!! then the object will lose only enough vertical distance so that the spyral trajectory really becomes a circle, and then the object will have become a satellite going forever and ever around earth and also "falling" forever and ever, but falling such a precise amount that it makes the object follow a circular trajectory.

Answer 3

Well, if the object is thrown on earth or any other body with a gravitational field, it will eventually hit the ground and stop any motion at all.

However, it should be noted that while the object is in flight, the horizontal velocity will not change, assuming no air resistance.

Answer 4

yep thats true!
the forces applied to a thrown object are the force of contact with air molecules(known as air resistance) and gravity.
when u throw the object u give it a certain velocity....(the velocity which your hand travelled the moment before letting go).
from there on supposing there's no air resistance the only force applied to the object is gravity which is applied at the vertical axis...this means it forms a 90 deegre angle with its horizontal movement thus having no effect on the objects horizontal acceleration...therefore not changing its horizontal velocity....!!!
so, until the moment that the object touches the ground its horizontal velocity remains unchanged....

Answer 5

The object may never hit the ground like a satellite. But its horizontal velocity is not constant because it moves on a circle.

So you dont only have to ignore the air resistance but you also have to suppose g to be constant which is not the case. I mean the g vector which always points to the center of the earth.

Answer 6

True

Only the vertical velocity is affected by gravity.

When an object hits a ground, ofcourse it will stop and thus the horizontal velocity becomes 0 but you always exclude that scenario in physics and mathematics.

Answer 7

1. You almost threw the book while reading Order of the Phoenix because of Umbridge's actions False 2. Some of the things Draco said about Harry were true True 3. Harry would be someone you can get along with False ( I just don't have the patience for that. =/ ) 4. Without Luna, the books wouldn't be the same True 5. Hermione annoyed you sometimes True 6. You felt bad for Bellatrix False 7. You cheered when Voldemort died True 8. Ron Weasley is great! True

Answer 8

You are partially correct. The velocity will not change UNTIL it hits the ground....Never is a long time.

You were incorrect in thinking your teacher would listen to you.

If the object were in space it would continue until something deflected or stopped it, but in space there is no horizontal nor vertical. Keep thinking sideways.

Answer 9

The problem begins when you define horizontal. It has sense when you consider a flat Earth... And then, surely, ground level puts a stop to the horizontal motion.
On round Earth, there are such speeds that make you not hit the ground.
But on the whole, it is not a general truth. So false.

Answer 10

the vertical velocity of an object will change due to gravity (it has an acceleration of 9.8 m/s^2) but the horizontal velocity never changes.