# Uncertainty Help!

**1. The problem statement, all variables and given/known data**

Students decide to measure a projectile’s range for an initial projectile angle of 45°. This angle has many advantages, not the least being that since the expression for the range is proportional to the sine of twice this angle, errors in determining the angle do not contribute to errors in the range.

As before, they make measurements to determine the initial speed. This time they find the initial speed to be 3.76 m/s with a relative uncertainty of 2.7%.

What is the uncertainty in the predicted range? [Remember that you can treat the uncertainty in the sin(2) factor as zero since it contributes no errors at 45°.]

_____ cm

**2. Relevant equations**

**3. The attempt at a solution**

I found the range to be 144cm and multiplied that by 2.7% to get 3.89 cm. But that’s apparently not the right answer.

http://ift.tt/1dV3E6B

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