[ssssss]

So, we can do nothing about the matter wave of a particle (although we can find its de Broglie wavelength)?

As far as your level is concerned,you dont have to go in Deep of it.Because for understanding matter waves you need to understand the Schrodinger Equation which is beyond your Scope.

[Winga]

If a question ask we to find the uncertainty of the position of a particle by providing the speed of a particle (e.g. 100 m/s) with a certain mass (e.g. 1kg), is it wrong?

The question should provide the uncertainty of the speed / momentum of the particle but not the exact speed / momentum of a particle, right?

[Demotivator]

I think in such questions, the implicit assumption is that p ~ dp, ie the uncertainty is roughly equal to the magnitude. Of course, that is hard to believe for a football but such approximations are made on the subatomic particles.

[Donaldson Tan]

Heisenberg's Uncertainty Principle is the quantitative bridge between de-broglie's equation and  wave-particle duality.

let's not talk about football but an electron in a one-dimensional box.

assuming we can see the electron with our naked eye,

In a closed box, the wave-particle duality of the electron allows the electron to be everywhere in the box (given it's a wave). since the electron is now everywhere, the electron (as a particle) must be moving in the box.

Opening the box gives us the position of the electron. The electron is stationery at one position inside the box. However, as a wave (when the box is closed), the electron is moving. Therefore, we conclude that we are uncertain of the momentum of the electron.

In fact, absorption/emmission spectra agrees with the uncertainty principle. we never get sharp lines, but peaks in the spectra.