Newton's Laws of Motion and Mechanics

Comprehensive practice flashcards covering Newton's laws of motion, types of mechanical forces, inertia, free body diagrams, momentum, units of force, and impulse.

How is weight defined in mechanics, and what are its formula and SI unit?

Weight is the force by which a body is pulled by gravity ($w = mg$). Weight is a force, not mass, and its S.I. unit is the Newton.

What is normal force?

When a body is pressed against a surface, it experiences a force that is perpendicular to the surface.

What is spring force, and how is it expressed mathematically?

When a spring is pressed, it opposes the change and produces a restoring force called spring force, given by $F = -k\boldsymbol{\alpha}$ (where $k$ is the spring constant).

What is tension?

When a string is pulled away from a fixed end, a restoring force is produced throughout the string; this restoring force is called tension.

What is friction force?

The force which opposes relative motion between two surfaces.

What is inertia?

The inherent property of a body by virtue of which it cannot change, by itself, its state of rest or the state of uniform motion along a straight line.

What is inertia of rest?

The tendency of the body to remain in its state of rest. It means a body at rest remains at rest and cannot start motion on its own.

What is inertia of motion?

The tendency of a body due to which it tries to remain in a state of uniform motion in a straight line, meaning it can neither accelerate nor retard on its own.

What is inertia of direction?

The inability of the body by virtue of which it tries to oppose any change in its direction of motion.

What does Newton's first law of motion state, and what is its alternative name?

A body at rest remains at rest and a body in motion remains in motion unless and until an external unbalanced force is exerted on it. It is also known as the Law of Inertia.

How does Newton's first law define force?

Force is that cause which changes or tends to change the state of the object.

What are the key steps and considerations when drawing a free body diagram (FBD)?

A body is treated as a point object, an observer must be chosen, and all forces exerted on the body must be shown.

How is linear momentum represented, and what type of physical quantity is it?

Linear momentum is represented by $p$ and is a vector quantity.

What is the CGS unit of force, and what is its relationship to the Newton?

The CGS unit of force is the dyne, and $1\,\text{Newton} = 10^{5}\,\text{dynes}$.

What are the SI and CGS gravitational units of force and their conversions?

The SI gravitational unit is $\text{kgf}$ ($1\,\text{kgf} = 1\,\text{kg} \times 9.8\,\text{m/s}^2 = 9.8\,\text{N}$), and the CGS gravitational unit is $\text{gf}$ ($1\,\text{gf} = 1\,\text{g} \times 980\,\text{cm/s}^2 = 980\,\text{dyne}$).

What is impulse, and how is it calculated?

Impulse is the product of average impulsive force and the short time interval during which it acts: $\text{Impulse} = \text{average impulsive force} \times \text{time duration}$.