標題:
問PHY 2000 CE MC Q.6 AND Q.7
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發問:
問PHY 2000 CE MC Q.6 AND Q.7 可唔可以解釋下個答案問黎?
最佳解答:
6. As the system is in equilibrium. So, the resultant force is zero in the system. Consider the vertical component. F2cos30° = 10 F2 = 11.5 N So, the answer is C. 7. As the inclined plane is rough, so frictional force exists. Frictional force always act on the direction which is opposed to the relative motion of the object. When the object moves upward, the downward component of the force is weight resolving along the plane + frictional force. When the object moves downward, the force is weight resolving along the plane - frictional force. So, the net force acting on the object is smaller in the latter case. So, the downward acceleration of the object is smaller when it moves downward. In a v-t graph, the magnitude of the slope is smaller when it moves downward. So, E is the answer.
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