S2.3 Concluding and evaluating Topic Practice

The density of a metal sphere is determined using a digital caliper and a mass balance.

The digital caliper is used to measure the diameter D of the sphere by placing the sphere in the jaws of the digital caliper. This reading is shown.

The sphere is then removed and another reading is taken immediately afterwards with the jaws closed.

State one way in which the procedure for the measurement of D can be improved using the same digital caliper.

A group of students is trying to determine the density and the viscosity of a liquid.

To determine the density, they use a balance to read the mass m of a sphere in air and immersed in the liquid.

They use a sphere of volume $V=1.827 \times 10^{-7} \mathrm{~m}^{3}$.
The readings are $m_{\text {air }}=1.427 \mathrm{~g}$ in air and $m_{\text {lmmersed }}=1.208 \mathrm{~g}$ in the liquid.
The readings are different due to buoyancy. The buoyancy force $F_{\mathrm{b}}$ is given by

where V is the volume of the sphere and $\rho$ is the density of the liquid.

Suggest a conclusion reached by the students.

An experiment is conducted to measure the specific heat capacity of water. A mass of water is placed in a glass beaker and energy is transferred from an electric heater.

The data collected are:

Mass of water $=(0.250 \pm 0.002) \mathrm{kg}$
Change in temperature of the water $=(14.0 \pm 0.5)^{\circ} \mathrm{C}$
Energy transferred from the electric heater $=(16000 \pm 300) \mathrm{J}$

Outline one source of systematic error in the experiment and its effect on the calculated value of the specific heat capacity of water. provided.

An experiment is conducted to measure the specific heat capacity of water. A mass of water is placed in a glass beaker and energy is transferred from an electric heater.

The data collected are:

Mass of water $=(0.250 \pm 0.002) \mathrm{kg}$
Change in temperature of the water $=(14.0 \pm 0.5)^{\circ} \mathrm{C}$
Energy transferred from the electric heater $=(16000 \pm 300) \mathrm{J}$

Outline one source of systematic error in the experiment and its effect on the calculated value of the specific heat capacity of water. provided.

A student investigates whether the Stefan-Boltzmann law, $L=4 \pi \sigma R^{2} T^{4}$, applies to stars.
L= luminosity of the star, in W
$\sigma=$ Stefan-Boltzmann constant
R= radius of the star, in m
T= surface temperature of the star, in K
To verify the law, they obtain values from databases and manipulate the data as shown.

Outline a conclusion for the investigation.

A student investigates whether the Stefan-Boltzmann law, $L=4 \pi \sigma R^{2} T^{4}$, applies to stars.
L= luminosity of the star, in W
$\sigma=$ Stefan-Boltzmann constant
R= radius of the star, in m
T= surface temperature of the star, in K
To verify the law, they obtain values from databases and manipulate the data as shown.

Outline a conclusion for the investigation.

A boat is moved from land to water by rolling it across a set of cylindrical airbags.

When fully inflated, an unloaded airbag has a diameter of 1.80 m and a length of 24.0 m . At a temperature of $15^{\circ} \mathrm{C}$, an airbag can hold 4200 mol of gas.

Identify an assumption used in this estimation.

The boat is then released to roll down across the airbags. When the boat loses contact with an airbag at the top of the slope, the airbag expands adiabatically.