[填空题]
In an experiment to determine the speed of sound in air, some students used a number of tuning forks of known frequencies and a tube with a moveable piston arranged as shown below.
For each tuning fork they used the setup shown in the diagram.
The students would sound the tuning fork, then move the piston slowly downwards until a loud sound is first heard. The length L was then measured. This was repeated for different tuning forks.
The graph shows the variation of $\frac{1}{L}$ with frequency.
1.Draw the line of best fit.
2.Calculate the fractional uncertainty of $\frac{1}{L}$ when the length is 20 cm.Fractional uncertainty =
3.(1)Determine the gradient, expressing your answer with the correct SI units.
(2)Use the gradient calculated in (i) to determine the speed of sound.v= $ms^{-1}$
