## HW 1B.27

$\Delta p \Delta x\geq \frac{h}{4\pi }$

Jessica Chen 2C
Posts: 103
Joined: Thu Jul 11, 2019 12:17 am

### HW 1B.27

Why is the uncertainty in velocity 5 m/s when given 5.00 ± 5.0 m/s, when in the example in the text they gave ±1.00mm/s and had the uncertainty as 2mm/s?

Matthew Chan 1B
Posts: 111
Joined: Sat Sep 07, 2019 12:16 am

### Re: HW 1B.27

There is an error in the solution manual. Check Dr. Lavelle's solution manual errors PDF on his website; he addresses that mistake.

https://lavelle.chem.ucla.edu/wp-conten ... rs_7Ed.pdf

Naji Sarsam 1F
Posts: 104
Joined: Sat Aug 17, 2019 12:18 am

### Re: HW 1B.27

In an uncertainty problem where they give a "variable" ± "a value", the uncertainty is twice that "value". This is easier to understand by example:

If a problem describes the velocity of an object as 5.00 m/s ± 1.00, the uncertainty would be double the value of 1.00, equaling an uncertainty of 2.00

This is because the symbol "±" indicates a range of values. In the case of the example above, the range of velocities the object could have is between 4.00 m/s and 6.00 m/s. Clearly then, there is a difference--or uncertainty--of 2.00 between the lowest possible velocity of 4.00 m/s and 6.00 m/s. This difference, again, can always be found by doubling the number after the "±" symbol.