Concise Physics Handbook

Newton's first law states: if no forces act on a body, or their resultant is zero, it maintains its state of rest or uniform rectilinear motion.

This formula describes how a force acting on a body causes its acceleration. It is the fundamental law of dynamics.

If one body acts on another, then the second acts on the first with a force equal in magnitude and opposite in direction. The law of interaction.

In a closed system, the total momentum is conserved: before and after interaction. The apostrophe means "after". This law works from atoms to spacecraft.

A force acting over time changes the momentum of a body. This is especially important in brief but powerful interactions — impact, shot, braking.

Momentum is the quantity of motion of a body, depending on its mass and velocity. The more massive and faster an object, the greater its momentum.

For a body to move in a circle, a force is needed that "pulls" it towards the center. It increases with mass and speed, and decreases with increasing radius. Used to describe satellites, carousels, turns on roads.

This is the minimum speed at which a body can move in orbit around a planet without engine thrust. For Earth, it's about 7.9 km/s. Derived from the equality of centripetal force and gravitational force.

The gravitational force between two bodies depends on their masses and the distance between them. This is a universal law acting throughout the Universe.

Weight is the force with which a body acts on a support. It differs from mass: it depends on gravity and is determined by m and acceleration g.

Friction force depends on the properties of the surfaces (μ) and the force with which the body is pressed against the surface (N).

Hooke's Law: deformation causes an elastic force that tends to return the body to its original state. The direction is opposite to the displacement.

Describes the "rotational effect" of a force. The greater the lever arm d, the easier it is to rotate the body with the same force.

On a flat surface, the support force is equal to the body's weight and balances the force of gravity, acting upwards.

The buoyant force of a fluid is equal to the weight of the displaced volume. It acts upwards and helps bodies float.

Pressure in a fluid increases with depth and depends on density ρ and gravity g. This formula is important for calculating buoyancy, density gradients, and pressure on the bottom of vessels. It is often used in conjunction with Archimedes' principle.