Topic 6.1: Experimental Skills Questions

Draw the point with its error bars.

The side of a cube is found with a caliper as 15.4 mm. Because a zero reading is subtracted, the side has an uncertainty of ±0.2 mm.

Calculate the percentage uncertainty in the side.

To find the spring constant of a spring, a student plots the applied force F (in newtons) on the y-axis against the extension x (in metres) on the x-axis and obtains a straight line through the origin.

State the SI units of the gradient of this graph.

Calculate the percentage uncertainty in the mass.

A video recorded at 60 frames per second shows a ball move 4.8 cm in 3 frames.

Calculate the speed of the ball.

A mass is recorded as 250 ± 5 g.

Calculate its fractional uncertainty.

A liquid's density is found to be ρ = 1.03 ± 0.04 g cm⁻³.

State the density and its absolute uncertainty in kg m⁻³, with appropriate precision.

A marker sinks to a depth d under a water pressure P, and theory predicts d = k√P.

To linearize the data the student plots depth d (vertical) against root-pressure √P (horizontal).

One table row reads P = 16.0 kPa and d = 5.2 cm.

Determine the coordinates of the point this row should be plotted at on the graph.

Draw a suitable best-fit line through the data.

A student times a ball falling from a fixed height five times and takes the mean.

Outline why the timing is repeated.

A glass microscope slide is about 1 mm thick, and its value is needed to 0.05 mm or better.

Suggest which instrument to use.

A string is 84.0 ± 0.2 cm long.

Calculate Δl/l for the string.

A nail is driven into wood.

The total length of the nail is measured with a ruler as 32.4 ± 0.1 cm and the length sticking out above the wood is 8.7 ± 0.1 cm.

The embedded depth is the difference of these two readings.

State the embedded depth and its absolute uncertainty.

Two power supplies are connected in series.

Their voltages are V₁ = 6.0 ± 0.3 V and V₂ = 9.0 ± 0.2 V.

State the total voltage of the combination and its absolute uncertainty.

A class is collecting data on how the pressure of a fixed gas sample depends on its volume, by pushing in a sealed syringe and reading a pressure gauge.

State one variable that must be controlled during the experiment.

In an experiment to find the resistivity of a metal rod, a student measures the rod's diameter with a micrometer at several different positions along its length and takes the mean.

Outline why the diameter is measured at several positions rather than just once.

Before plotting a sin(i) against sin(r) graph for a refraction experiment, a student needs to finish processing the data.

One row records the angle of refraction as r = 42.0°.

Calculate the value of sin r to be entered in that row, giving your answer to three significant figures.

Activity follows ln A = ln A₀ − λt. A graph of ln A against t is drawn.

State how ln A₀ is found from the graph.

A ray of light passes from air into a glass block.

A student uses a protractor with a resolution of 1° to measure the angle between the refracted ray and the normal.

State this measured angle and its absolute uncertainty if the refracted ray crosses the protractor scale at the 33° mark.

In a double-slit experiment the fringe separation s is measured for several screen distances D.

Theory predicts s = (λ/a)·D, where λ is the wavelength and a is the slit separation.

The student plots s on the vertical axis and wants a straight line through the origin so the gradient gives λ.

State the quantity that should be plotted on the horizontal axis.