## Uncertainty in percentage

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

Chinyere Okeke 2J
Posts: 88
Joined: Wed Sep 30, 2020 10:05 pm
Been upvoted: 1 time

### Uncertainty in percentage

What is the uncertainty when it is in percentage. Like for example, if a problem says an e- has a velocity of 4.5 m/s with an uncertainty of 1% is the delta-v 1 or is it 4.5(0.01)?

John Pham 3L
Posts: 138
Joined: Wed Sep 30, 2020 9:49 pm
Been upvoted: 4 times

### Re: Uncertainty in percentage

That should be correct. You just multiply the percentage to the value given to find the uncertainty.

Leo Naylor 2F
Posts: 106
Joined: Wed Sep 30, 2020 9:42 pm
Been upvoted: 1 time

### Re: Uncertainty in percentage

The delta-v is 4.5(0.01), as you guessed. Multiply the percentage uncertainty by the velocity to find the absolute uncertainty.

Christine Ma 3L
Posts: 87
Joined: Wed Sep 30, 2020 9:35 pm

### Re: Uncertainty in percentage

Whenever you're unsure, you can also use the units to help you. Uncertainty in velocity (Δv) should have the units m/s so you would multiply the % by the velocity to get the uncertainty in velocity in meters per second. Hope this helps.

Khoa Vu 3l
Posts: 86
Joined: Wed Sep 30, 2020 9:59 pm

### Re: Uncertainty in percentage

Adding on to what the other posts have said, multiplying your velocity by the decimal form of your percentage should yield the change in velocity. However, you should keep in mind that for uncertainties, the uncertainty can be both additive and subtractive. For example, the 1% uncertainty of 4.5 is .045. This could mean that the velocity is either 4.545 or 4.455. You would need to find the difference between these two velocities in order to get the absolute velocity change.

Posts: 95
Joined: Wed Sep 30, 2020 9:41 pm

### Re: Uncertainty in percentage

The percentage uncertainty represents the percent of the originally velocity that is uncertain. So in this case it would be 4.5 m/s +/- 0.01(4.5 m/s)

IshanModiDis2L
Posts: 84
Joined: Wed Sep 30, 2020 9:49 pm

### Re: Uncertainty in percentage

That should be correct but I would also suggest using the units to check your work when doing it.

Kyle Dizon 3A
Posts: 91
Joined: Mon Oct 05, 2020 12:16 am

### Re: Uncertainty in percentage

Relying on the units will help with your confusion. Also, you can attempt to multiply the percentage to find the value of the uncertainty.

Susanna Givan 2B
Posts: 61
Joined: Thu Feb 27, 2020 12:16 am

### Re: Uncertainty in percentage

Multiplying is the correct procedure, then? Thank you so much for your clarification, it really helped me understand percentage uncertainty.