How is this force the weight?

[thestormpetrel]

I was solving on of the physics problems on the mcatquestionoftheday site and i am having trouble understanding the explanation of this problem:
http://mcatquestionoftheday.com/physics/fly-like-an-eagle/
I don't understand how the force=pressure/area is equal to the weight.
i mean pressure on the area of door is being applied by the molecules, so the force IS coming from the air molecules and not gravity. The force also doesn't seem to be opp to gravity, acc to my understanding anyway. Help? Thanks 🙂

---

Members don't see this ad.

 

[gettheleadout]

The question is poorly written. They are not equating the collective force upon the door (due to air pressure) to weight (a force of gravity), but they are attempting to relate that force to the equivalent force of gravity on a mass of X. This mass is what the question is asking for.

However, the question doesn't make any sense because it asks "to pull open the door...is equivalent to moving how many metric tons?"

This question was clearly written by someone with a substandard understanding of physics, because I can "move" a mass of a million metric tons with a gentle push if my position is fixed and the mass is on a frictionless surface. Mass represents inertia, which is not a resistance to motion per se, but a resistance to acceleration; there is no minimal force required to "move" any given mass - the requisite force depends on the desired acceleration. Any non-zero force will effect motion of a body provided there are no other forces present, the question is simply how much motion.

What the question means to ask is "the minimal force required to pull open the door...is equivalent to the force required to support what mass against gravity?" or something of the sort.

Considering this question was provided by the Gold Standard prep company, it makes me concerned about the quality of their material. Bad move, GS.

 

[texan2414]

Just one question weakens the credibility of their prep material?

 

[gettheleadout]

Just one question weakens the credibility of their prep material?

When they've chosen these questions to provide for free through the Question A Day site, it's presumed that we are intended to judge their material based on these samples. I would be sure to avoid throwing potential customers flawed questions as freebies. So, in my opinion, we have an issue here of not only material error, but negligence or laziness in the conduct of the company.

But honestly, who cares? I've already taken the test, it doesn't matter to GS that I'm disinclined from using their material. You're free to hold an equally valid opinion on GS of whatever nature you prefer, I'm simply commenting on my perception. I have very high standards for products and services in general.