Two particles of masses $$$0.8 \mathrm{~kg}$$$ and $$$0.2 \mathrm{~kg}$$$ are connected by a light inextensible string that passes over a fixed smooth pulley. The system is released from rest with both particles $$$0.5 \mathrm{~m}$$$ above a horizontal floor (see diagram). In the subsequent motion the $$$0.2 \mathrm{~kg}$$$ particle does not reach the pulley. Show that the magnitude of the acceleration of the particles is $$$6 \mathrm{~m} \mathrm{~s}^{-2}$$$ and find the tension in the string. ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................

Mathematics

IGCSE&ALevel

CAIE

Exam No：9709_w20_qp_41 Year：2020 Question No：5(a)

Answer:

$0.8 g-T=0.8 a, \quad T-0.2 g=0.2 a$,
For system: $0.8 g-0.2 g=(0.8+0.2) a$
Attempt to solve for either $a$ or $T$
$a=6 \mathrm{~ms}^{-2}$ and $T=3.2 \mathrm{~N}$

Knowledge points:

4.2.4 use appropriate formulae for motion with constant acceleration in a straight line. （Questions may involve setting up more than one equation, using information about the motion of different particles.）

4.4.4 solve simple problems which may be modelled as the motion of connected particles. e.g. particles connected by a light inextensible string passing over a smooth pulley, or a car towing a trailer by means of either a light rope or a light rigid tow- bar.

Answer:

Knowledge points:

Solution:

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