jjj

@jjj@lemmy.blahaj.zone

• ⁨Comment⁩ on ⁨⁩ ⁨⁨1⁩ ⁨week⁩ ago⁩:

  xkcd.com/1251/ (there is always an xkcd about it)

• ⁨Comment⁩ on ⁨Is this physics correct?⁩ ⁨⁨1⁩ ⁨week⁩ ago⁩:

  Ah, my mistake.

• ⁨Comment⁩ on ⁨Is this physics correct?⁩ ⁨⁨2⁩ ⁨weeks⁩ ago⁩:

  Your equations are correct (although as I said in my other comment 9.81 is the global average but gravity varies by ~0.1 so that’s too many significant figures), but their issue doesn’t have to do with using sloped distance (they don’t as far as I can tell). It says the height change is 2 meters, and they use 2 meters as the distance since that’s the component of the displacement parallel to gravity. The problem is that they didn’t convert mass to weight.

  work = force • displacement = |force| * |displacement| * cos(angle between them)
      = component of force parallel to displacement * |displacement|
      = component of displacement parallel to force * |force|
  
  weight = force due to gravity = mass * acceleration due to gravity ≈ 5 kg * 9.8 m/s² = 49 N
  

• ⁨Comment⁩ on ⁨Is this physics correct?⁩ ⁨⁨2⁩ ⁨weeks⁩ ago⁩:

  Not quite, you have to multiply distance by the force applied to the object (its weight in Newtons), but they’re using its mass (kilograms).

  It’s actually 98 Nm, since weight = mass * gravitational acceleration and g ≈ 9.8 m/s².

• ⁨Comment⁩ on ⁨Not that limit⁩ ⁨⁨3⁩ ⁨weeks⁩ ago⁩:

  The first one is incorrect, the limit doesn’t exist unless you specify whether you’re coming from the left or right.

  On another note, I think their student has invented a new symbol for “Does Not Exist”.