If an athlete moves faster, what happens to her momentum?

Question

a. It decreases
b. Velocity has no impact on momentum.
c. Her momentum equals zero.
d. It converts to impulse

Answer 1

her momentum increases. i think d is the best answer.

Answer 2

1

Answer 3

The answer is D. impulse is a change in momentum. when the athlete moves faster, the momentum increases. This is a poorly done question (must be from a text or workbook) however that is the best answer

Answer 4

Momentum = mass x velocity so if velocity increases so does the momentum.
Of these I would choose d as the correct one (only if I HAD to choose one)...the other three are way off the correct answer.
F = ma...this is the impulse

as velocity changes...there is acceleration so mv becomes ma
which is the impulse.

Answer 5

The "best" of these four answers, though it pains me to use that excesively generous description, is "d. It converts to impulse." However, this simple statement is DEEPLY FLAWED, and merits much more careful analysis.

It is actually a peculiar, and to my mind positively misleading statement. Let me show you why.

If she moves faster, her momentum will certainly HAVE INCREASED. That much is obvious and certain. (I am assuming that in the interim she has not sweated so much that her loss in mass REDUCES her momentum more than the increase in speed increases it. I presume that that is a safe assumption!)

However, she has RETAINED the momentum that she already had, and has merely ADDED to it. So the question that I think is being asked is actually WRONG, both as a matter of logic and simple English, but also as a question of science.

It SHOULD have said "What happens to her INCREASE in momentum?" (I trust that you can see the significant difference here.) For the scientific fact is that there is a connection (equality!) between the INCREASE in momentum and a force that WAS applied to something for some particular time, which technically WAS (not : "will BECOME") an IMPULSE only in the limit that the time of application tended to zero while the product of Force x Time of Application remained finite in this now past event..

O.K., now we've got that straight, here is the next point. It is misleading to even say that "her increase in momentum converts to impulse," because that very statement INVERTS CAUSE AND EFFECT! Her increased momentum is a CONSEQUENCE of an IMPULSE, it's not CONVERTED INTO THAT IMPULSE.

What IS true is that her increased momentum comes as a result of an impulse she receives from pressing harder with her feet on the ground, in a direction opposite from that in which she is running. Therefore, she has accelerated and increased her momentum while at the same time necessarily (i) imparting a minuscule (possibly impulsive) TORQUE to the Earth, thereby affecting its rate of spin, however minute that change in spin rate might be, and (ii) imparting some minuscule LINEAR momentum to the Earth also --- both of these being in the OPPOSITE sense from the effects that SHE experienced.

But I would again argue that it is a misuse of English, and a misleading summary of the science of this situation, to say that her "increase in momentum" has "converted" to anything. She simply possesses that extra momentum; the question of its "conversion" to anything simply doesn't arise until she chooses to do SOMETHING ELSE with it, in the future.

Her increase in m omentum has ARISEN because of something that happened, but that is VERY DIFFERENT from "CONVERTING" it to anything. What one can say accurately is this:

Her increase in momentum came at the expense of corresponding (if minute) changes in both the angular and linear momenta of the Earth. The agency by which those changes were made, both to her own and the Earth's motional states, was a pair of equal and opposite forces, possibly meeting the definition of "impulses" between her feet and the Earth's surface. The impulse between her and the Earth (if such it was) will have imparted to the Earth an equal and opposite change in linear and/or angular momentum.

I think that that is what the original setter of this question had in mind. However, to phrase it so BADLY suggests that that person is EXTREMELY CONFUSED about scientific cause and effect. I can only hope that the person setting this question is not a supposedly scientific educator, for I shudder at the idea of having someone so confused having anything to do with the education of the young.

Let me try to put the essential points in the starkest possible way:

IMPULSE CONVERTS TO MOMENTUM where acceleration is concerned; but if the athlete runs into a barrier and knocks it over, then MOMENTUM CONVERTS TO IMPULSE.

Live long and prosper.

Answer 6

Her momentum increases, and is converted into impulse.

Answer 7

the mometum = velocaty x mass of an object so an icreas in velocaty increases her momentum

Answer 8

None of the above, her momentum increases. Get a GCSE physics book, and look it up.
Stop expecting other people, who have already done their homework, to do yours for you!!!!!!!
Oh yeah, I am a science teacher

Answer 9

Crap question - none of the given answers is correct. As she moves faster her momentum increases, provided her mass remains constant.

Answer d is only correct if she collides with something, exerting a force on it.

Answer 10

momentum is mass*velocity.
therefore as she moves faster, momentum increases.
impulse is change in momentum.
hence, momentum converts to impulse
answer is (d)