Definitions & Concepts

A

Air Resistance

Air resistance, also known as drag, is a force that acts opposite to the direction of motion of an object moving through a fluid, such as air. It occurs because the moving object collides with air molecules, creating friction and pushing back against the object's movement. In the context of sports, including tennis, air resistance affects how fast a ball or object travels and can influence its trajectory.

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E

Energy

Energy in physics is the ability to do work or cause change. It can exist in various forms, such as kinetic energy (energy of motion), potential energy (stored energy due to position or configuration), and more. The key characteristic of energy is that it can be transferred from one object or system to another and can change from one form to another, but it cannot be created or destroyed (this is known as the law of conservation of energy).

F

Force

A force is an external factor which can change the state of rest or state of uniform motion of an object. It can cause an object to accelerate, change direction, or change shape. Forces are vector quantities, meaning they have both magnitude (strength) and direction. The unit of measurement for force is the newton (N) in the International System of Units (SI).

Types of forces important in tennis:
• Gravitational Force: The force that attracts two bodies with mass toward each other. For example, Earth's gravity pulls objects toward its center.
• Normal Force: The support force exerted upon an object that is in contact with another stable object (e.g., a book resting on a table).
• Frictional Force: The force resisting the relative motion of two surfaces in contact.
• Tension Force: The force transmitted through a string, rope, cable, or similar object when it is pulled tight by forces acting from opposite ends.

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I

Impulse

Impulse is a concept in physics that refers to the change in momentum of an object when a force is applied over a period of time. It is the product of the force applied and the duration of time over which the force is exerted.

J

K

Kinetic Energy

Kinetic energy is the energy possessed by an object due to its motion. When an object moves, it has the ability to do work because of its velocity and mass. The faster it moves and the more massive it is, the more kinetic energy it has.

L

M

Magnitude

Magnitude refers to the size or amount of a quantity, without considering its direction. It is a scalar property, meaning it only expresses how much of something there is, but not which way it is oriented or the vector path it follows.

Momentum

Momentum describes the quantity of motion an object has. It is a vector quantity, meaning it has both magnitude and direction, and depends on two factors: an object's mass and velocity.

N

O

Object

An object is any item or entity that can be observed, analyzed, or acted upon by physical forces. It is an object in the sense of being a distinct entity with mass and volume, and can be either animate or inanimate. Objects are considered in the context of their interactions with forces, their motion, and their properties.

P

Potential Energy

Potential energy is the energy that an object possesses due to its position, condition, or state. Unlike kinetic energy, which is associated with motion, potential energy is stored energy that has the potential to do work when it is released.

Power

Power in physics refers to the rate at which work is done or energy is transferred. It measures how quickly energy is used or converted from one form to another.

Q

R

S

Speed

Speed is a scalar quantity that refers to how fast an object is moving without considering the direction of motion. It is the rate at which distance is covered over time. Unlike velocity, which includes both speed and direction, speed only measures how quickly an object moves regardless of its direction.

Strength

Strength refers to the ability of a material or an object to withstand forces without breaking or deforming. It is a measure of how much stress a material can handle before failure.

T

Torque

Torque is a measure of the rotational force applied to an object. It describes the tendency of a force to cause an object to rotate around an axis. Essentially, torque is what makes objects spin or rotate when a force is applied at a distance from the axis of rotation.

U

V

Velocity

Velocity is a vector quantity that refers to the rate at which an object changes its position over time, in a specific direction. Unlike speed, which only measures how fast an object is moving, velocity includes both the magnitude (how fast the object is going) and the direction of motion.

W

Work

Work is defined as the transfer of energy that occurs when a force is applied to an object, causing it to move. It is a measure of how much force is exerted over a certain distance. The unit of work is the joule (J), where 1 joule is equal to 1 newton of force applied over a distance of 1 meter (1 J = 1 N·m).

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