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Question
In a situation the contact force by a rough horizontal surface on a body placed on it has constant magnitude. If the angle between this force and the vertical is decreased, the frictional force between the surface and the body will
Options
increase
decrease
remain the same
may increase or decrease.
Solution
decrease
According to the first law of limiting friction,
f = μN
where f is the frictional force
N is the normal reaction force
μ is the coefficient of static friction
and
N = mg － Fcosθ
where m is the mass of the body
F is the contact force acting on the body
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