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 1.increase. 2.decrease 3.remains the same 4.may increases or decreases

Answer 1

Dear student
as we know that contact force is resultant of normal force and frictional force and the angle between contact force and normal defines the angle of friction
hence if contact force is constant and angle from frictional force is increased component of net force along the surface that is frictional force decreases
$$\begin{gathered} \sin \theta =\frac{frictionforce}{contactforce} \\ frictionforce=contactforce\left(\sin \theta \right) \\ if\theta decreasesthenfrictionalforcedecreases \end{gathered}$$

Regards