Dynamics - Physics Notes

Physics Notes – Dynamics

Understanding the forces that govern motion in our universe

Physics Mechanics Dynamics Newton's Laws Education

Dynamics is the branch of mechanics that deals with the study of forces and their effects on motion. While kinematics describes how objects move, dynamics explains why they move.

Core Concepts

Understanding Force

A force is any interaction that, when unopposed, will change the motion of an object. Forces can cause:

• An object at rest to start moving
• A moving object to stop
• A moving object to change direction
• An object to change shape (deformation)

F = m × a (Force = mass × acceleration)

Unit: Newton (N) where 1 N = 1 kg·m/s²

Force Demonstration

Adjust the force to see how it affects the object's motion:

Force (N): 0 N

With no force applied, the object remains at rest (Newton's First Law).

Types of Forces

• Gravitational Force - Attraction between masses (weight)
• Normal Force - Support force exerted by a surface
• Tension Force - Force transmitted through strings/ropes
• Frictional Force - Opposes relative motion between surfaces
• Applied Force - Direct push or pull on an object
• Air Resistance - Frictional force from air molecules
• Spring Force - Restoring force from compressed/stretched springs

Example: When you push a book across a table, you're applying an applied force. The table exerts a normal force upward, gravity pulls downward, and friction opposes the motion.

Newton's Laws of Motion

First Law – Law of Inertia

An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

Inertia is the tendency of an object to resist changes to its state of motion. Mass is a measure of an object's inertia.

Second Law – Force and Acceleration

The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass.

ΣF = m × a

Where ΣF is the net force (sum of all forces acting on the object).

Third Law – Action-Reaction

For every action, there is an equal and opposite reaction.

Example: When you walk, your foot pushes backward on the ground (action), and the ground pushes forward on your foot (reaction), propelling you forward.

Applications of Dynamics

• Transportation: Car safety (seatbelts, airbags), airplane flight
• Sports: Projectile motion in basketball, friction in skiing
• Engineering: Bridge design, building stability
• Space Exploration: Rocket propulsion (Newton's Third Law)
• Everyday Life: Walking, pushing a cart, throwing a ball

Key Takeaways

• Forces cause changes in motion (acceleration)
• Newton's Laws describe fundamental principles of motion
• All forces occur in pairs (action-reaction)
• Friction always opposes relative motion
• Mass measures inertia (resistance to changes in motion)

Further Study

Explore more physics topics on our educational blog:

Download PPT

© 2023 EduVerse Education | Share this post: