Understanding Forces in Action for A Level Physics

Types of Forces In physics, forces are responsible for changing the motion or shape of an object. There are several types of forces: Gravitational force : The a...

Types of Forces

In physics, forces are responsible for changing the motion or shape of an object. There are several types of forces:

Equilibrium Conditions

An object is in equilibrium when the vector sum of all forces acting on it is zero. There are two conditions for equilibrium:

  1. Translational equilibrium: The sum of all forces in any direction is zero (∑F = 0)
  2. Rotational equilibrium: The sum of all torques (moments) about any point is zero (∑τ = 0)

Force Analysis

Force Diagrams

Force diagrams are visual representations of all forces acting on an object, drawn using vectors.

Worked Example

Problem: Draw a force diagram for a box resting on an inclined plane.

Solution: The forces acting on the box are:

Resolution of Forces

Forces can be resolved into components along perpendicular axes using vector analysis.

Moments and Torque

Torque (τ) is the tendency of a force to cause rotational motion about a pivot point. It depends on the force magnitude, direction, and moment arm (perpendicular distance from the pivot).

Centre of Gravity and Centre of Mass

The centre of gravity is the point at which the entire weight of an object is considered to act. For uniform gravitational fields, it coincides with the centre of mass.

Principle of Moments

The principle of moments states that for an object in rotational equilibrium, the sum of clockwise moments equals the sum of anticlockwise moments about any pivot point.

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📚 Category: A Level Physics AS
Last updated: 2025-11-03 15:02 UTC