Two particles, A (mass 0.2 kg) and B (mass 0.3 kg), are attached to an inexstensible string which passes over a smooth pulley. A initially rests on a sloping roof that makes a 30 degree angle with the horizontal and B hangs freely below the roof. Find the acceleration, a, of the particles when released from rest.(adsbygoogle = window.adsbygoogle || []).push({});

(I tried to draw a diagram but it came out looking a mess).

My workings (T is the tension in the string):

(1) 0.3g - T = 0.3a

(2) T - 0.2g sin 30 deg = 0.2a

(1) T = 0.3g - 0.3a

(2) 0.3g - 0.3a - 0.1g = 0.2a

(2) 0.5a = 0.2g

(2) a = 0.4g

taking g to be 9.8 m/s/s:

a = 3.92 m/s/s

My book says 7.84 m/s/s.

What did I do wrong?

Thanks for any help.

Jimi

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# Simple particles and motion

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