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# M1 lift/pulley question

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1. In part one, you set up silmataenous equations in terms of tension and acceleration for p and q&r respectively, however according to the mark scheme, for the scale pan you don't take into account the reaction forces of r on q to find an overall equation like you would in a normal lift question? Are you meant to count the different masses as one or am I just simply doing my working incorrectly?
2. (Original post by neutraltones)
In part one, you set up silmataenous equations in terms of tension and acceleration for p and q&r respectively, however according to the mark scheme, for the scale pan you don't take into account the reaction forces of r on q to find an overall equation like you would in a normal lift question? Are you meant to count the different masses as one or am I just simply doing my working incorrectly?
Huh? I think there are reaction forces but you're looking at the scale pan as a whole system not the weights so you still only include the tension in the string and the total weight of the masses.
https://2802a3b1a650824d2586fd3336bd...%20Edexcel.pdf
^^question 3 there for those who can't see OP's picture
3. neutraltones
Both methods fundamentally work. In this example the blocks P and Q accelerate at the same rate. Given that this is true they can be assumed to act as a single mass of mass 15kg. Ultimately the mark schemes method is a simplification of the problem.

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