Physics Quiz: Forces and Equilibrium

Forces and Equilibrium

• A force can be transferred along its line of action without changing its effect on a body.
• The horizontal and vertical components of a force can be calculated using trigonometric methods.
• Displacement is a scalar quantity.

Types of Forces

• Reaction force: the force exerted by a body against a surface in contact with it.
• Resultant force: the sum of all forces acting on a body.
• Equilibrant force: the force needed to maintain equilibrium.

Equilibrium

• A body in equilibrium may be in translational or rotational motion.
• The sum of the forces and moments about any point is zero for a body to be in equilibrium.
• Conditions for a body to be in translational equilibrium: ∑Fx = 0, ∑Fy = 0, and ∑Fz = 0.
• The moment of a force about a point is minimum when the force acts perpendicular to the point.

Moments

• The moment of a force about a point is the product of the force magnitude and the distance from the point to the line of action of the force.
• The moment of a couple is the same about all points.
• A couple is formed by two parallel forces with the same magnitude but opposite direction.

Units of Force and Moment

• The unit of force in the International System of Units (SI) is the Newton (N).
• The unit of moment is the Newton-meter (N-m).

Resolving Forces

• The graphical method, analytical method, and trigonometric method can be used to resolve forces.
• The moment method is not a method for resolving forces.