In an experiment to measure the acceleration of free fall a student ties two different blocks of masses m1 and m2 to the ends of a string that passes over a frictionless pulley. The student calculates the acceleration a of the blocks by measuring the time taken by the heavier mass to fall through a given distance. Their theory predicts that a = g(m1 - m2)/(m1 + m2) and this can be re-arranged to give g = a(m1 + m2)/(m1 - m2).

error in $m_1+m_2$ is $1\%$ OR error in $m_1-m_2$ is $40\%$ OR error in a is $1\%$ ✓ adds percentage errors ✓ so error in $g$ is $42\%$ OR $40\%$ OR $41.8\%$ ✓

$g=9.996$ «$\mathrm{m\ s^{-2}}$» OR $\Delta g=4.20$ «$\mathrm{m\ s^{-2}}$» ✓ $g=(10 \pm 4)$ «$\mathrm{m\ s^{-2}}$» OR $g=(10.0 \pm 4.2)$ «$\mathrm{m\ s^{-2}}$» ✓

the acceleration would be small/the time of fall would be large ✓ easier to measure /a longer time of fall reduces the % error in the time of fall and «hence acceleration» ✓