The Heisenberg Uncertainty Principle?

Question

Suppose the minimum uncertainty in the position of a particle is equal to its de Broglie wavelength. If the particle has an average speed of 4.2 105 m/s, what is the minimum uncertainty in its speed?
______m/s

Answer 1

The scale used in measuring the average velocity as 4.2*10^5 m/s can measure, with highest precision, only the smallest (least count) change in speed as 0.1*10^5 m/s

So the observed value will be either
(4.2 - 0.1)*10^5 = 4.1*10^5 m/s
or
(4.2 + 0.1)*10^5 = 4.3*10^5 m/s

The smallest error in measurement of speed with highest precision of available means qualifies to be called as the “minimum uncertainty in speed” = 0.1*10^5 m/s

so as the famous quote below, the "uncertainty" or the precision of the measurement is + or - 0.1*10^5 m/s centered around the average of 4.2*10^5 m/s

The error in measurement of speed

{{{{{famous Quote}}}}: with link

The uncertainty relations involve the uncertainties in the measurements of these variables. The "uncertainty" -- sometimes called the "imprecision"--is related to the range of the results of repeated measurements taken for a given variable. For example, suppose you measure the length of a book with a meter stick. It turns out to be 23.6 cm, or 23 centimeters and 6 millimeters. But since the meter stick measures only to a maximum precision of 1 mm, another measurement of the book might yield 23.7cm or 23.5 cm. In fact, if you perform the measurement many times, you will get a "bell curve" of measurements centered on an average value, say 23.6 cm. The spread of the bell curve, or the "standard deviation," will be about 1 mm on each side of the average. This means that the "uncertainty" or the precision of the measurement is plus or minus 1 mm.

Answer 2

I'm not sure.