As shown in the figure, the fixed smooth surface in the elevator has an inclination angle of 30 ° and the lower end of the spring on the inclined surface is connected with a wood block with a mass of M = 4kg. When the elevator descends at an acceleration of 2m / S ^ 2, the elevator will be able to move forward seek Spring force Write the support of the face to the block
Let the elastic force be f and the supporting force be n
From Newton's second theorem
F=(mg-ma)*sina=16N
N = (mg MA) * cosa = 16 * radical 3N
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