## General question 1B.27

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

Simon Dionson 4I
Posts: 107
Joined: Sat Sep 14, 2019 12:17 am

### General question 1B.27

I had a general question on what it means when the velocity is given as
5.00 + or - 5.0 m*s^-1. If we are using p=mv for momentum, how could I relate the + or - interval into ΔP?

AVerma_F19
Posts: 59
Joined: Thu Jul 25, 2019 12:15 am
Been upvoted: 1 time

### Re: General question 1B.27

Δp = m Δv is the equation to relate Δv to Δp. I believe that the Δ accounts for +/-.

Amy Luu 2G
Posts: 105
Joined: Wed Sep 18, 2019 12:19 am

### Re: General question 1B.27

+ or - represents the uncertainty so you would use 5.0 in the equation delta x >= h/(4pi)(5.0 m/s)(mass). In this equation, 5 is the uncertainty in the velocity.

Ryan Narisma 4G
Posts: 104
Joined: Fri Aug 30, 2019 12:18 am

### Re: General question 1B.27

Hi Simon Dionson 4I! So the uncertainty in velocity is given by a $\pm$5.0 m/s. Let's say the velocity given was 10 m/s. Then velocity COULD be 15 m/s OR 5 m/s. The range (in statistics) of this is the uncertainty in velocity. So the uncertainty in velocity—$\Delta$v— is equal to 10 m/s. It is not 5.0 m/s, as Amy Luu 3L has mentioned. I think there is an error in the solutions manual so use the following link to get the correct answer for this question: https://lavelle.chem.ucla.edu/wp-conten ... rs_7Ed.pdf. I hope this helps!

Shutong Hou_1F
Posts: 117
Joined: Sat Sep 14, 2019 12:17 am

### Re: General question 1B.27

± 5.00 m*s^-1 means that the uncertainty (the range of possible values of speed) in speed is 5.00 m*s^-1, rather than that the speed is really positive or, unreasonably, negative.