How to Calculate Time and Uncertainty for Rotating Pulsars

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In summary, the pulsar rotates 1.400 806 448 872 75 times in 30.0 days, with an associated uncertainty of +/- 5 ms.
  • #1
scmejla
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Hello, perhaps you could help with a problem.

Suppose a pulsar rotates once every 1.400 806 448 872 75 + or - 5 ms, where the trailing + or - 5 indicates the uncertainty in the last decimal place (it does not mean + or - 5ms).

a. How many times does the pulsar rotate in 30.0 days?
I solved this one, 30days(60s/min)(60min/hr)(24hr/day) = 1.85(10^9)

b. How much time does the pulsar take to rotate 2.0(10^6) times?
(Give your answer to at least 4 decimal places.)

c. What is the associated uncertainty of this time?

It's these last two that are giving me issues, for b. I figured you just multiply the amount of rotations by the time it takes to rotate, I came up with 2801.61 s but according to webassign is wrong. I even stuffed it with 2 zeros to go out 4 decimal places. I'm just not sure about c, though I need the answer to b. to start.
 
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  • #2
scmejla said:
Hello, perhaps you could help with a problem.

Suppose a pulsar rotates once every 1.400 806 448 872 75 + or - 5 ms, where the trailing + or - 5 indicates the uncertainty in the last decimal place (it does not mean + or - 5ms).

a. How many times does the pulsar rotate in 30.0 days?
I solved this one, 30days(60s/min)(60min/hr)(24hr/day) = 1.85(10^9)
Your notation is misleading! (30)(60)(60)(24)= 2592000. Then you multiplied by 1000 ms/s and divided by 1.400 806 448 872 75 ms.

b. How much time does the pulsar take to rotate 2.0(10^6) times?
(Give your answer to at least 4 decimal places.)

c. What is the associated uncertainty of this time?

It's these last two that are giving me issues, for b. I figured you just multiply the amount of rotations by the time it takes to rotate, I came up with 2801.61 s but according to webassign is wrong. I even stuffed it with 2 zeros to go out 4 decimal places.
What do you mean "stuffed it with 2 zeros? 2(10^6)= 2000000 and since you are multiplying by approximately 1.4, you should get about 2800000.
I get 2801612.8977455.

I'm just not sure about c, though I need the answer to b. to start.
1.400 806 448 872 75 + or - 5 ms, could be as large as 1.400 806 448 872 75 +5 = 1.400 806 448 872 80 ms or a small as 1.400 806 448 872 75 -5 = 1.400 806 448 872 70 ms. Do your calculation using each of these, then find the average of the two extremes. The uncertainty will be that average + or - something.
 
  • #3
Thank you for your help, you've led me to the correct answer. It is 2801.6128977455, you must have left out the (ms) or 10^-3 when multiplying. My calculator was only set up to display 6 digits. Thanx again.
 

1. What is the purpose of a changing units problem?

A changing units problem is used to convert a measurement from one unit to another. This is helpful when working with data that is given in different units or when comparing measurements from different sources.

2. How do you convert units in a changing units problem?

To convert units, you can use conversion factors or unit conversion tables. First, identify the starting unit and the desired unit. Then, multiply the measurement by the appropriate conversion factor to get the converted value.

3. What are some common units that are used in a changing units problem?

Common units that are used in a changing units problem include length (meters, feet, inches), mass (grams, kilograms, pounds), volume (liters, gallons, cubic meters), and temperature (Celsius, Fahrenheit, Kelvin).

4. Why is it important to check your units when solving a changing units problem?

It is important to check your units to ensure that the final result is in the correct unit. This helps to avoid errors and ensures that the final answer makes sense in the context of the problem.

5. What are some strategies for solving a changing units problem?

Some strategies for solving a changing units problem include setting up a conversion factor equation, canceling out units using dimensional analysis, and using unit conversion tables. It is also helpful to label and keep track of units throughout the problem.

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