Mechanics

Mechanics is the branch of physics concerned with the motion of objects and the forces that cause or change that motion. It is conventionally divided into kinematics, which describes motion in terms of position, velocity and acceleration without reference to its cause, and dynamics, which links motion to the forces acting on a body. Classical mechanics, built on the work of Isaac Newton, accurately predicts the behaviour of everyday objects moving at ordinary speeds.

Newton's three laws form the foundation of the subject. The first states that an object remains at rest or in uniform motion unless acted on by a net force. The second relates the net force on a body to the product of its mass and acceleration. The third states that for every action there is an equal and opposite reaction. From these principles one can analyse how forces combine and how objects respond.

Many distinct forces appear in mechanical problems. Gravity attracts masses toward one another and gives objects weight near the Earth. Frictional force opposes relative sliding between surfaces, tensional force acts along stretched ropes and cables, and the normal force supports objects against a surface. Engineers apply these ideas to structures such as bridges, where loads must be balanced, and to aerodynamics, where moving air exerts lift and drag. Energy and momentum provide complementary tools for predicting outcomes without tracking every force in detail.

Frequently asked questions

What is the difference between kinematics and dynamics?

Kinematics describes how objects move using quantities like velocity and acceleration. Dynamics explains why they move by relating motion to the forces acting on them.

What does Newton's second law state?

It states that the net force on an object equals its mass multiplied by its acceleration, so a larger force or a smaller mass produces greater acceleration.

What is friction?

Friction is a force that opposes the relative sliding of surfaces in contact. It converts some kinetic energy into heat and is essential for walking, braking and gripping.