Edexcel A-Level Physics Materials

Use of $\rho=m / V$

- $\rho$ between 8000 and $8600 \mathrm{~kg} \mathrm{~m}^{-3}$

Allow ecf for V from 1(a) for both marks.

Example of calculation

$\rho=m / V$$\rho=0.0098 \mathrm{~kg} / 1.18 \times 10^{-6} \mathrm{~m}^{3}$$\rho=8300 \mathrm{~kg} \mathrm{~m}^{-3}$

EITHER

- Calculates values for 2% range of the density of brass

- Statement comparing this with 1(b) and relevant conclusion made (1)

OR

- Calculates percentage difference between 8550 kg m^-3 and the density from 1(b)

- Statement comparing this with 2% and relevant conclusion made (1)

Example of calculation

8550 kg m^-3 x 1.02=8721 kg m^-38550 kg m^-3 x 0.98=8379 kg m^-3

(Use balance to measure) mass and multiply mass by g to determine weight

Or

Use the balance set to read newtons to determine weight (of ball)

Measure the diameter (of the ball) (with the calliper) to determine volume

Identify upthrust with weight of fluid displaced

Calculate the weight of fluid displaced by multiplying the volume of the ball by the density of the liquid and g

Use F = 6πηrv.

η = 2.2 × 10² Pa s.

Example: 1.1 × 10⁻² N = 6π × η × 0.50 × 10⁻² m × 5.4 × 10⁻⁴ m s⁻¹, so η = (1.1 × 10⁻²)/(6π × 2.7 × 10⁻⁶) = 216 Pa s.