Apply Newton's second law for an object at rest on Earth and analyse t

1.	Apply Newton's second law for an object at rest on Earth and analyse the result.
Answer» Solution : The OBJECT is at rest with respect to EARTH (INERTIAL coordinate SYSTEM). There are two forces that act on the object. (i) Gravity acting downward (negative y-direction) (ii) Normal force by the surface of the Earth acting upward (positive y-direction) The FREE body diagram for this object is vec F_g = - mg hatj ` vecF = N hatj ` But there is no acceleration on the ball. So `veca = 0` . By applying Newton.s second law`(vecF_("net") = mvec a )` Since `vec a = 0 , vecF_("net")=-mg hatj + N hatj ` `(-mg + N) hatj = 0` By comparing the components on both sides of the equation, we get ` - mg + N = 0` N = mg ` We can conclude that if the object is at rest, the magnitude of normal force is exactly equal to the magnitude of gravity.

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