# Gravity...........

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#### jschaef5

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2 balls of different mass are dropped from the same height.<br />(a)the lesser mass one hits the ground first<br />(b) more mass one hits first<br />(c) hit at same time<br />(d) neither hit<br /><br /><br />Would i be correct if i answered b since the one with more mass is pulling the earth/ground more than the lesser mass one. I know the teacher was looking for c but wouldn't B be the real answer?<br /><br />Since he didn't say the masses; one ball could be the size of a peanut and the other the size of the moon in which case it would be evident that they don't hit at the same time.<br /><br />Or am I wrong? <br /><br />I answered c since I knew that's what the teacher wanted. <div class="Discussion_UserSignature"> </div>

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#### tfwthom

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The Big Misconception<br /><br />An earlier section of this lesson, stated that the acceleration of a free-falling object on Earth is 10 m/s/s. This value (known as the acceleration of gravity) is the same for all free-falling objects regardless of how long they have been falling, or whether they were initially dropped from rest or thrown up into the air. Yet the question is often asked "Doesn't a massive object accelerate at a greater rate than a less massive object?". This question is a reasonable inquiry that is probably based upon personal observations made of falling objects in the physical world. After all, nearly everyone has observed the difference in rate of fall of a single piece of paper (or similar object) and a textbook. The two objects clearly travel to the ground at different rates – with the massive book falling faster. <br /><br />The answer to the question (Doesn't a massive object accelerate at a greater rate than a less massive object?) is . . . absolutely not! That is, absolutely not, if you are considering the specific type of falling motion known as free-fall. Free-fall is the motion of objects under the sole influence of gravity; free-falling objects do not encounter air resistance. Massive objects will only fall faster than less massive objects if there is an appreciable amount of air resistance present. <br /><br />More info: http://www.physicsclassroom.com/Class/1DKin/U1L5a.html<br /> <div class="Discussion_UserSignature"> <font size="1" color="#3366ff">www.siriuslookers.org</font> </div>

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#### jschaef5

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actually u have to take into effect that the object also has gravity and is pulling the earth with a greater force, so if u combine the 2 the bigger massed object would have a greater velocity then the smaller <div class="Discussion_UserSignature"> </div>

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#### the_id

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The object with the greater mass also has a greater resistance to acceleration <i><b>because</b></i> of that mass, which would cancel out it's increased "pull" on the object towards which it was falling.

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#### tfwthom

##### Guest
Based on the question:<br /><br />2 balls of different mass are dropped from the same height. <br />(a)the lesser mass one hits the ground first <br />(b) more mass one hits first <br />(c) hit at same time <br />(d) neither hit <br /><br />The weight of the object is not taken into account.<br /><br />Suppose that an elephant and a feather are dropped off a very tall building from the same height at the same time. We will assume the realistic situation that both feather and elephant encounter air resistance. Which object - the elephant or the feather - will hit the ground first?<br /><br />Most people are not surprised by the fact that the elephant strikes the ground before the feather. But why does the elephant fall faster? This question is the source of much confusion (as well as a variety of misconceptions). <br /><br />The elephant and the feather are each being pulled downward due to the force of gravity. When initially dropped, this force of gravity is unbalanced by all other forces; and thus, both elephant and feather begin to accelerate (i.e., gain speed). As the elephant and the feather fall and begin to gain speed, they begin to encounter the upward force of air resistance. Air resistance is the result of an object plowing through a layer of air and colliding with air molecules. The more air molecules which an object collides with, the greater the air resistance force. Subsequently, the amount of air resistance is dependent upon the speed of the falling object and the surface area of the falling object. Based on surface area alone, it is safe to assume that (for the same speed) the elephant would encounter more air resistance than the feather.<br /><br />But why then does the elephant, which encounters more air resistance than the feather, fall faster? After all doesn't air resistance act to slow an object down? Wouldn't the object with greater air resistace fall slower?<br /><br />Answering these questions demands that we combine our understanding of Newton's first and se <div class="Discussion_UserSignature"> <font size="1" color="#3366ff">www.siriuslookers.org</font> </div>

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#### zavvy

##### Guest
What you're failing to take into account is that nobody really knows what Gravity is despite all those fancy equations...<br /><br /><img src="/images/icons/smile.gif" /> ....and Newton was an Alchemist. <br /><br />www.alchemylab.com<br /><br />www.indiana.edu<br /><br />www.cftech.com<br /><br />

S

##### Guest
Bad question as no start times stated.<br />Seems the answer (c) presupposes they were dropped simultaneously. If true: then, (c) as the size of the object matters not. Your answer (b) presupposes the drop start time was different. If dropped simultaneously the larger object may pull the earth but the distance clearly appertains to the smaller object too. Now what about the drag of the smaller object by the larger...

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#### igorsboss

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The next question sholud have been "why?"...<br /><br />Why?<br />There is more gravitational force on the more massive object, because it has more gravitational mass. However, the more massive object will resist being accelerated more, because it has more inertial mass.<br /><br />Experiments show that gravitational mass and inertial mass are equialent. So, when we calculate the acceleration of each object, we find that the gravitational mass always cancels the inertial mass.<br /><br />Hence we find that each object accelerates the same way, regardless of mass.<br /><br />(I agree the question has many many loopholes)

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#### heyscottie

##### Guest
jschaef:<br /><br />Cutting through most of the posts above that didn't really answer your question, you are actually right.<br /><br />Two objects falling with different masses taking the same amount of time to strike the earth presupposes that the falling objects are miniscule with respect to the earth. The acceleration they impart on the earth is effectively ignored. A larger object will move the earth toward it somewhat more, meaning it will strike in a shorter amount of time.<br /><br />Of course, this effect is not measurable until we start talking about extremely large masses, ones that are decent fractions of the size of the earth itself. So practically speaking, everything falls at the same rate. In pure theory, however, the more massive object still falls at the same rate but hits sooner because it ends up having a shorter distance to fall.<br /><br />Scott

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#### jschaef5

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like siarad said, its a bad question and can be looked at in different scales... so if you have two balls that fit in your hand it wouldn't affect it but if you have two large bodies like a moon and a planet it would.<br /><br />Thanks all. <div class="Discussion_UserSignature"> </div>

S

##### Guest
As I said before, not if dropped at the same time as the reduced distance would surely apply to both.

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#### heyscottie

##### Guest
siarad:<br /><br />That's why I was careful to avoid using the phrase "dropped at the same time"!<br /><br />Scott

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