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Question 19M.3.SL.TZ1.b.i

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Date May 2019 Marks available [Maximum mark: 2] Reference code 19M.3.SL.TZ1.b.i
Level SL Paper 3 Time zone TZ1
Command term Explain, State Question number b.i Adapted from N/A
b.i.
[Maximum mark: 2]
19M.3.SL.TZ1.b.i

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 m 1 − m 2 m 1 + m 2 and this can be re-arranged to give  g = a m 1 + m 2 m 1 − m 2 .

In a particular experiment the student calculates that a = (0.204 ±0.002) ms–2 using m1 = (0.125 ±0.001) kg and m2 = (0.120 ±0.001) kg.

There is an advantage and a disadvantage in using two masses that are almost equal.

State and explain the advantage with reference to the magnitude of the acceleration that is obtained.

[2]

Markscheme

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» ✔

Do not accept ideas related to the mass/moment of inertia of the pulley.

Examiners report

Q 1 b) was quite well answered. Only the weakest candidates presented difficulty in understanding simple mechanics.

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