Edexcel A-Level Physics Arithmetic and Numerical Computation

Which of the following derived units can be expressed in SI base units as $\mathrm{kg} \mathrm{m}^{2} \mathrm{~s}^{-3}$ ?

A student investigated the photoelectric effect using the apparatus shown.

He used a source of white light and colour filters to shine different wavelengths $\lambda$ of light onto the photocell.

Photoelectrons were emitted with a range of kinetic energies, creating a small current in the photocell.

Using the potentiometer, the student varied the potential difference across the photocell. As the potential difference across the photocell increased, the current in the photocell decreased.

He measured the potential difference $V_{\mathrm{s}}$ when the current in the photocell was zero.
He calculated the maximum kinetic energy $E_{\text {max }}$ of the photoelectrons for each wavelength of light.

The table shows the student's data.

Calculate the percentage difference between h and the accepted value for the Planck constant.

Percentage difference =

A student investigated the bending of a plastic beam.

The beam, of width w and height h, was supported at either end by two metal rods a distance l apart, as shown.

She applied a force F to the middle of the plastic beam by hanging a mass from it.

The beam bent downwards as shown.

She measured the vertical distance d moved by the middle of the plastic beam and repeated this measurement for increasing values of F.

She recorded her results in a table, as shown.

The student’s teacher suggested that using a plastic beam with a smaller value of h would improve the measurement of d.

Justify the teacher’s statement.