Applejack’s fat.

@Background Pony #2423  
Yeah, but the problem there is that they’re essentially assuming a spherical pony. They’re oversimplifying the model to the point where it no longer resembles the actual situation. We can assume our physical laws apply in Equestria, but we must acknowledge that others do as well.

I think tensile strength goes down significantly when it expands like that.

If that vine was as tough as people seem to think it is, according to this theory Applejack would have broken the window trying to cut the vine.

@ze  
Pegasi have ultralight bones as a rule, the butterflies don’t have to be all that dense to hold up a seriously thin filly.

@Kj2  
GUYS. PONIES ARE MADE FROM DARK MATTER.
 
SO ARE BUTTERFLIES.

@Kj2  
Applejack’s mutant powers include having bones made from obsidian as well as a healing factor and bone claws.  
And before you ask why her brother doesn’t showcase a mutant power, remember that, according to Apple Family Reunion, Applejack’s actually adopted.

@Mayojar77  
‘Only Applejack’  
I cant think on Applejack being that ‘overweight’ and still look normal, i d say that if not all ponies then at least earth ponies must be insanely heavy

@FanOfMostEverything
 
As I understand it…
 
Any physics class will ground in its students that the laws of physics are universal - i.e. for them to to be acknowledged as such, they have to apply everywhere a physicist or physics student can apply them. (The concept that ‘physics might work differently here’ is regarded as either either extremely theoretical conjecture or, more likely, a joke.)
 
Extending the laws of physics (as we understand them) to another universe is therefore a short leap of deduction; this applies even said universe can be plainly observed to work differently, under the assumption that ‘there are a few extra things we can safely ignore here’, or in certain very limited circumstances(such as when some known physics variable appears to be derivable, i.e. Applejack’s mass).

@Kj2  
That’s only Applejack.

Why do people always think equations of physics in a nonmagical environment apply in Equestria?

@Background Pony #8809  
Considering the size of pegasi wings I always assumed the local gravity field to be somewhere around 3-4 meters per second or roughly equivalent to Mars.

Why are we assuming acceleration due to gravity is 9.8? We have no idea how big their planet is. Is that just based on the earth ponies in Hearth’s Warming Eve calling the land “Earth”, and assuming it’s the same planet?

the big problem here is who the hell can they now how tough the vine is?
 
they’re almost more like full on trees than just vines, and we all knows trees vary wildly in hardness.

17400 kg is ~18tons not 19, but still mlp ponies are made of dark matter or what?

She applied 50 tons of force. She doesn’t have to weigh 50 tons to apply the force, she just has to be able to apply a moment. Given how many assumptions you’ve already made you may as well assume she can stick her hooves to the ground.
 
Now calculate how strong her bones must be to act as anchors for muscles that are capable of applying 50 tons of force.