- #1
lavoisier
- 177
- 24
Hi everyone, a very simple problem that is nevertheless baffling me, probably because I'm no physicist and I lack method in tackling it.
A few days ago I was on my way home from the airport, and I was carrying a trolley suitcase, a bit like this one:
http://www.google.be/imgres?imgurl=...oVeXRIIeNsgHl1oPwBw&tbm=isch&ved=0CFQQMygsMCw
The suitcase weighed about 10 kg, but it occurred to me that when I stopped (with the suitcase still tilted at an angle, not resting vertically) the weight acting on my hand was surely much less than 10 kg.
When I got home, I got out that little thingy that you use to weigh suitcases (a sort of dynamometer?), I attached it to the handle (fully stretched out) and tilted the suitcase at various angles from the ground, checking the corresponding weight.
If you measure the angle between the ground and the line passing through the handle and the wheels touching the ground, at 90° of course there was no weight because the suitcase was resting. Still no weight at a particular angle a bit smaller than 90° (probably at the point where the centre of gravity lay on the vertical line from the wheels), then increasingly larger weight (up to about 4 kg) as the angle decreased to about 50°, I reckon. What surprised me was that the weight didn't increase any further. I was expecting it to get larger and be maximal at a very small angle.
I reasoned that the weight of the suitcase acts on its centre of gravity, which is probably close to the geometric centre of the 'main' body. The suitcase is static when this weight is balanced by the reaction of the ground plus the force exerted by the person on the handle. What I can't figure out is how the various forces distribute and where they act. For instance, I think I remember from physics I at university that the reaction from the ground always acts vertically. But then, wouldn't that completely counterbalance the weight, which is also acting vertically? What component of the weight causes the suitcase to spin and fall if you don't hold it? Etc.
So, could anyone please point me to some information concerning the static forces acting on a trolley suitcase (or a related case) depending on the angle it forms to the ground?
Thanks!
L
A few days ago I was on my way home from the airport, and I was carrying a trolley suitcase, a bit like this one:
http://www.google.be/imgres?imgurl=...oVeXRIIeNsgHl1oPwBw&tbm=isch&ved=0CFQQMygsMCw
The suitcase weighed about 10 kg, but it occurred to me that when I stopped (with the suitcase still tilted at an angle, not resting vertically) the weight acting on my hand was surely much less than 10 kg.
When I got home, I got out that little thingy that you use to weigh suitcases (a sort of dynamometer?), I attached it to the handle (fully stretched out) and tilted the suitcase at various angles from the ground, checking the corresponding weight.
If you measure the angle between the ground and the line passing through the handle and the wheels touching the ground, at 90° of course there was no weight because the suitcase was resting. Still no weight at a particular angle a bit smaller than 90° (probably at the point where the centre of gravity lay on the vertical line from the wheels), then increasingly larger weight (up to about 4 kg) as the angle decreased to about 50°, I reckon. What surprised me was that the weight didn't increase any further. I was expecting it to get larger and be maximal at a very small angle.
I reasoned that the weight of the suitcase acts on its centre of gravity, which is probably close to the geometric centre of the 'main' body. The suitcase is static when this weight is balanced by the reaction of the ground plus the force exerted by the person on the handle. What I can't figure out is how the various forces distribute and where they act. For instance, I think I remember from physics I at university that the reaction from the ground always acts vertically. But then, wouldn't that completely counterbalance the weight, which is also acting vertically? What component of the weight causes the suitcase to spin and fall if you don't hold it? Etc.
So, could anyone please point me to some information concerning the static forces acting on a trolley suitcase (or a related case) depending on the angle it forms to the ground?
Thanks!
L