Forces in Action: Types, Equilibrium, and Analysis
Types of Forces There are several types of forces that act on objects in the physical world: Gravitational Force : The attractive force between any two masses d...
Types of Forces
There are several types of forces that act on objects in the physical world:
Gravitational Force: The attractive force between any two masses due to gravity.
Electromagnetic Force: The attractive or repulsive force between charged particles or between magnets.
Normal Force: The force exerted by a surface on an object in contact with it, perpendicular to the surface.
Friction Force: The resistive force that opposes the motion of an object sliding over a surface.
Tension Force: The pulling force exerted by strings, cables, or other flexible connectors.
Elastic Force: The restoring force exerted by a deformed elastic material like springs.
Equilibrium Conditions
For an object to be in equilibrium (stationary or moving with constant velocity), the vector sum of all forces acting on it must be zero.
For translational equilibrium (no linear acceleration): ΣF = 0
For rotational equilibrium (no angular acceleration): Στ = 0
Force Analysis
Force Diagrams
Force diagrams are useful for visualizing all the forces acting on an object. Each force is represented by a vector arrow.
Resolution of Forces
Forces can be resolved into components along perpendicular axes to analyze their effects separately.
Moments and Torque
Torque (τ) is the turning or twisting force caused by a force acting at a distance from a pivot point. It depends on the force (F), perpendicular distance from the pivot (r), and is given by: τ = Fr
Centre of Gravity and Mass
The centre of gravity is the point where the weight of an object appears to act, while the centre of mass is the point through which the object's mass is evenly distributed.
Worked Example: Inclined Plane
Problem: A 10 kg box rests on a plane inclined at 30° to the horizontal. Find the normal and friction forces acting on it if the coefficient of friction is 0.3.
Solution:
Draw a free-body force diagram with the block's weight (W = 98 N), normal force (N), and friction force (f).
Resolve W into components parallel and perpendicular to the plane: Wparallel = 98 sin(30°) = 49 N, Wperp = 98 cos(30°) = 84.9 N
For translational equilibrium, ΣFparallel = 0 ⇒ f = 49 N