FN<\/sub>=mg<\/p>\n where m is the mass in kg and g=-9.8N\/kg on Earth’s surface.<\/p>\n Example:<\/strong> Calculate the normal force acting on a 1.2kg textbook lying flat on a table.<\/p>\n Solution:<\/strong> FN<\/sub>=mg=(1.2)(-9.8)=-11.76N or -12N in significant digits. The negative sign just means the force of gravity is downwards.<\/p>\n If the object is lying on a sloped surface, the normal force is no longer straight down; rather, it acts perpendicular to the angle of the slope. Trigonometry is required, in such a case, to calculate the normal force.<\/p>\n Example:<\/strong> Calculate the normal force acting on a 40.kg object lying on a 27\u00ba incline.<\/p>\n Solution:<\/strong> We are best off to draw a diagram:<\/p>\n Notice that, in the red triangle, FN<\/sub> is adjacent to the 27\u00ba angle. The hypotenuse is mg=-392. Therefore,<\/p>\n FN<\/sub>=mgcos27o<\/sup>=-392cos27o<\/sup>=-349.3N=-350N in sig digs<\/p>\n It only makes sense that, as the incline gets steeper, the normal force diminishes. The gravitational force shifts toward pulling the object down the incline instead.<\/p>\n![\"Normal](\"\/..\/normf0.png\")
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