Question: What is the uncertainty of the rubber band strectch (x ± ?) and the un

Question

Question: What is the uncertainty of the rubber band strectch (x ± ?) and the uncertainty of the weight of the coins (w ± ?). Please see the image attached for the data collected during my experient.

Here was the experimental setup (incase it is helpful to know): For this experimental, I attached one end of a rubber band to a fixed support and attached a small plastic bag to the other end of the rubber band. I measured the initial length of the rubber band (19.6 cm) then added one 10 cent coin into the bag which caused a stretch in the rubber band. I measured and recorded this new length. I repeated this process adding more and more coins into the plastic bag and measuring the length of the rubber band each time. Force was calculated as weight of coins w = nmg and stretch of the rubber band was calculated using: new length - initial length = stretch.

Explanation / Answer

See, to get the uncertainty in x or W, you don't need to provide the data table.

You have measured the stretch x using a ruler. Moreover because it involves difference between initial length and final length, you needed to two measurements (i.e., initial length and final lelngth) to get each x. So the uncertainty in x si just 2*(minimum deviation in the ruler).

As probably you used a meter stick to measure x values. Minimum deviation or minimum length that you can measure in a meter stick is 1 mm = 0.001 m. So the uncertainty in each x measurement is 2*.001 m=.002 m. That is why the large values of x in your data table are more reliable compared to the small ones like x=0.001 m or x=0.002 m.

Simlarly you measure the mass of the 10 cent coin using a balance. See what is the minimum mass you can measure there. That will be the uncertainty in the mass (you have to write that in kg unit).

As w=mass*g (and you take g=9.81 m/s^2, the standard value used)

so the uncertainty in w will be (uncertainty in mass in kg)*9.81 N.

Related Questions

Navigate

• Browse (All)
• Browse Q
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.