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# AS/A-Level Mechanics question-pls help!! watch

1. "A block of mass 4kg rests on a smooth plane inclined at so degrees to the horizontal. It is connected by a light, inextensible string passing over a smooth pulley at the top of the slope to a 3kg particle hanging freely. Find the acceleration of the system and the tension in the string."

I don't understand how the angle comes into it because the string is parallel to the slope? This is my working:

T=4a
3g-T=3a
Therefore a = 4.2m/s/s
2. When it says parallel to the slope the string is actually at the same angle as the slope. So first what needs to be taken into account to is the forces acting on the body. If one were to the system as one body then one needs to take the total forces on the body. So first the weight of 3kg would act as a pulling force on the body and force would be mg, of the particle.If there are no more forces pulling the body in the same direction then there take into account forces oppposing the motion. which would be the weight of the block on the slope. The force acts parallels to the slope. So it would be acomponent of the weight. so the esultant force would give u the acceleration.

Weight of particle; 3*9.8=29.4
Component of force = sinangle* mg of block
resultant force = ma

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Updated: March 30, 2016
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