Which one is easier to lift 1kg of steel or 1kg of feather?

Answer 1

It's a trick question, but with a not-so-trick answer:

The expected "correct" answer, is that since both "weigh" 1kg, they both have the same weight, and so neither one is heavier.

The CORRECT answer actually depends on a few more details, which will be explained in steps as follows:

1) The kg is a unit of mass, whilst weight, in the correct meaning of the word, is a measurement of forcemeasured in Newtons.

2) Force = mass x acceleration

-> Weight = mass x acceleration-due-to-gravity (g = 9.81 m/s2)

So up until now, we could argue that the iron and the feathers each have a weight of approx. 9.81 Newtons. However, so far we've only calculated the downward force on the two objects due to gravity.

Assuming that we're measuring the weight of these two objects somewhere on Earth, we must also consider the effects of the Earth's atmosphere, specifically the upward force this causes. Since air is a fluid, we must consider the effects of upthrust on these two objects:

3) Upthrust = weight-of-displaced-fluid

Now this is where things start to get interesting! Since we can safely assume that iron is more dense than feathers, then for the two objects to have the same mass of 1kg, the volume of the feathers must be greater than the volume the iron. Therefore, they will displace more of the fluid (air):

4) Iron-upthrust < Feathers-upthrust

So, getting back to weight:

5) Weight = downforce-due-to-gravity - upthrust-from-fluid

So, since the downforce due to gravity is equal in both instances, BUT the feathers produce more upthrust, the weight of the iron is, in fact, greater than the weight of the feathers.

Therefore, if they are both measured at the same location on Earth, 1kg of iron will be heavier than 1kg of feathers.

(Just don't tell your school Physics teacher this, unless you want him to think you're a smart-ass :-)

Answer 2

Under normal circumstances, the iron, as the feathers, being loosely packed, will (1) present a much larger volume to lift, and (2) tend to move around when you try to pick them up. This assumes that the feathers are contained in something light - if they aren't contained then it will be effectively impossible to lift them at all. I am also assuming that the iron is in one piece (since it's stated that the feathers are loosely packed, it seems reasonable to assume that if there was anything remarkable about the packing of the iron - for example, it is in the form of ball bearings - then that would be remarked on in the question, which it isn't). Also, if the iron is very hot or very cold, that could make it much more difficult to lift. However, assuming no special circumstances like those, the iron would be fairly easily lifted by a person of average strength (you can get 10kg iron dumbbells for weight training - it may be tiring to lift them if you're not very strong, but most people can) while the feathers would take up so much volume that you would probably need the assistance of another person, or some sort of mechanical device, to lift them - not because they're heavy, just because they're awkward.

Answer 3

Neither. Since they both have a weight of 1kg (kilogram) one cannot be heavier than the other.

Answer 4

Both are equally easy to lift because they both weigh 1kg. The difference lies in the volume - lifting 1kg of feathers would require more space due to their lower density compared to steel.

Answer 5

both the same

Answer 6

they're both one kilogram so....

Answer 7

10kg of iron

Answer 8

10 kg of feathers