Forces and Motion - Lecture Notes

Vocabulary flashcards covering force, motion, Newton’s laws, and friction with definitions.

Force

A push or pull acting on an object.

Newton (N)

Unit of force in the metric system.

Effects of Force

Can move a stationary object, stop a moving object, change speed, change direction, or change the shape of an object.

Contact Forces

Forces that require direct contact between objects (e.g., muscular force and frictional force).

Muscular Force

Force applied using muscles.

Friction

The resistive force that opposes motion between two surfaces in contact.

Non-contact Forces

Forces that act at a distance without direct contact (e.g., gravitational, magnetic, and electrostatic forces).

Gravitational Force

The force of attraction between Earth and objects, pulling toward the Earth's center.

Magnetic Force

The force between magnets or magnetic materials.

Electrostatic Force

The force between charged objects.

Buoyant Force (Upthrust)

Upward force exerted by a fluid on an immersed object; explains why objects float or rise. Also called Upthrust.

Motion

Change in position of an object with time.

Rectilinear Motion

Motion in a straight line.

Circular Motion

Motion around a fixed point.

Periodic Motion

Motion that repeats after equal time intervals (e.g., pendulum).

Rotational Motion

Motion when an object spins about its axis.

Newton's First Law (Law of Inertia)

An object at rest stays at rest and an object in uniform motion stays in motion unless acted on by a net external force.

Inertia

The resistance of any physical object to a change in its state of motion or rest.

Newton's Second Law

The rate of change of momentum is proportional to the applied force; commonly expressed as F = m × a.

F = m × a

Equation relating force, mass, and acceleration.

Newton's Third Law

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

Static Friction

Friction that prevents the starting of motion between two surfaces at rest.

Sliding Friction

Friction that acts when an object slides over a surface.

Rolling Friction

Friction that occurs when an object rolls; usually less than sliding friction.

Fluid Friction (Drag)

Friction that opposes motion through a fluid (air or water).

Advantages of Friction

Provides braking power and traction; helps in walking, enables vehicle grip, and supports writing.

Disadvantages of Friction

Causes wear and tear, produces heat, and reduces the efficiency of machines.

Ways to Reduce Friction

Use lubricants, ball bearings, polish surfaces, and adopt streamlined shapes.

Lubricants

Oils or greases that reduce friction between surfaces.

Ball Bearings

Rolling elements that reduce friction by converting sliding motion to rolling.

Polished Surfaces

Smoothing surfaces to reduce friction.

Streamlined Shapes

Designs that reduce drag and improve efficiency (e.g., cars, planes).