Errors, uncertainties and error barsAQA A-Level Physics: Mind map

Exam questions on Errors, uncertainties and error bars

1. A student measures the diameter of a wire with a micrometer screw gauge that reads to the nearest 0.01 mm. With the jaws closed and nothing between them, the gauge reads 0.02 mm. The student then measures the diameter at five different places along the wire and the readings vary slightly, between 0.41 mm and 0.45 mm.
   Explain why calculating the mean of the readings taken at the five places reduces the effect of random error but does not remove the zero error.2 marks
2. A student determines the density of a metal cube. The mass of the cube is 85.0 ± 0.5 g and the length of each side is 2.00 ± 0.02 cm.
   Calculate the percentage uncertainty in the density of the metal.2 marks
3. A student times 20 complete oscillations of a simple pendulum of length 0.800 ± 0.002 m. The time for 20 oscillations is 35.9 ± 0.4 s. The acceleration of free fall can be found from g = 4π²L/T², where T is the period of the pendulum.
   Calculate the period T of the pendulum and its absolute uncertainty.3 marks