Giving Scientific Presentations

JB20120403

   

Prologue: Giving Bad Talks

   

   

   

Topics

● General guidelines● Miscellaneous advice● Sample presentation

   

General Guidelines

● 10-12 minutes, w/ 3 minutes Q & A

– Questions mandatory!● Save Powerpoint, Open Office Impress, et cetera

presentations in .pdf format

– Give HM and JB an electronic copy in advance● Choose within lab teams who will talk on which

experiment.● Please arrange a meeting with HM/JB (as

appropriate) to review your talk.

   

General Guidelines

● Talks should follow this rough outline:

– Title Page (1 slide)– Intro (background and theory) (~1-2 slides)– Experimental Method (~2-3 slides)– Data and Analysis (~2-3 slides)– Discussion (~1-2 slides)– Conclusion (1 slide)

   

Miscellaneous Advice

● Graphics– Readable– Balance text and figures

● Be aware of time– Overall length of presentation– Remember – multiple input paths– About one minute per slide– Rehearse!

● Nervousness

   

Sample Presentation

   

Measurement of the Acceleration Due to Gravity

John BelzApril 3, 2012

   

Outline

● Acceleration due to gravity● Method: The simple pendulum● Description of data analysis● Discussion of results● Concluding remarks

   

Background● Galileo asserted that in the

absence of air resistance all objects fall with the same constant acceleration.

● More recent experiments have confirmed this to an accuracy of a few parts in a billion:

– S. Carusotto et al., Phys. Rev. Lett. (1992).

– S. Chu et al., Nature (1999).

● What is this acceleration g?

   

Measuring g; Free-Fall Experiments

● Measure distance fallen over some time interval

● d = ½ gt2

● Difficulties:– Precise

measurement of distance

– Wind resistance becomes significant

   

Measuring g; Pendulum Experiments

● The period of oscillation is dependent on g

● Air resistance negligible

● Random error can be controlled by measuring over many oscillations.

   

The Simple Pendulum

   

Data and Analysis

● Measure with a stopwatch the time it takes for the pendulum to complete 20 oscillations. Do this ten times, and take the average to find the period T of oscillation.

● Do this for several values of the length l.● Plot l versus T2, and g is proportional to

the slope.

   

Experimental Data

● Result of averaging over 10 20-oscillation trials.

   

Linearize and Fit to Extract g

● Perform weighted linear least-squares fit to determine slope

● Best fit gives g = 979.3 ± 3.0 cm/s2

● 2 = 4.79, 3 D.O.F.

● p-value = 0.19. Model is supported by the data.

   

Discussion● Good agreement with

linear l vs T2 model

● Residuals indicate random error well understood, no significant systematic effects at this level.

● Uncertainty in length dominates; longer pendulum would have better error in relative height.

● Averaging over more periods can improve timing uncertainty.

   

Conclusion

● The simple pendulum is a useful tool for measuring the acceleration due to gravity.

● Measured g = 979.3 ± 3.0 cm/sec2

● Suggested improvements to random and systematic uncertainties have the potential to improve precision of result.

   

Schedule

● Tues 3rd April: This lecture● Fri 6th April: Complete Lab #3● Fri 13th April: Submit Lab #3 reports● Mon 9th – Mon 16th April: Arrange meeting

with instructor to review presentation. ● Tues 17th April: Oral Presentations