Edexcel A-Level Physics AS Units in Calculations

Pearson Edexcel International Advanced Subsidiary/Advanced Level in Physics, Issue 3, July 2021Physics XPH11/YPH11

Review units in calculations in Edexcel A-Level Physics through SI base-unit derivations, derived quantities and unit checks from data.

How this is tested

identify SI base units for derived quantities such as farads, watts and tesla
show formula units by substituting base or derived units into calculation expressions
check whether table units are consistent by calculating values such as current from R = V/I

[Maximum number: 2]

A student investigated the flow of water through a horizontal pipe using the apparatus shown.

Figure for Question 2(a) — Edexcel A-Level Physics AS

The mass M of water leaving the pipe in a time t is given by the formula

M=\frac{\pi \rho P r^{4} t}{8 \eta L}

where
$\rho=$ density of water
P= pressure difference between the ends of the pipe
r= internal radius of the pipe
$\eta=$ viscosity of water
L= distance between digital pressure gauges

Show that the formula gives the unit for $\eta$ as $\mathrm{Nsm}^{-2}$ .

How this is tested

Question 2(a)