IB Sports, exercise and health science Topic B.2.1.1 Linear Motion and Linear Kinematics in Sport Revision Notes (SL/HL)

IB Sports, exercise and health science Topic B.2.1.1 Linear Motion and Linear Kinematics in Sport Revision Notes (SL/HL) | RevisionDojo

Written by official IB examiners

Definition

Kinematics

Kinematics is the branch of mechanics that studies motion without considering the forces that cause it. It focuses on describing motion using parameters such as position, displacement, speed, velocity, and acceleration.

Definition

Motion

Motion is the change in position of an object or body over time. It can involve movement from one location to another or changes in the position of individual body parts relative to each other. Motion is described using key concepts such as displacement, velocity, and acceleration.

Motion can be:

Linear (motion in a straight line), such as a sprinter running down a track.
Curvilinear (motion along a curved path), such as a football being kicked in a long arc.
Angular or rotational (motion around an axis), such as a figure skater spinning on one foot.
General (a combination of linear and angular motion), such as a cyclist pedaling while moving forward.

Definition

Linear Motion

Linear motion refers to movement along a straight path.

Vectors and Scalars

A scalar has size only, such as distance, speed, mass, and time.
A vector has both size and direction, such as displacement, velocity, acceleration, force, momentum, and impulse.
Vectors with the same direction add simply, while vectors in different directions must be combined geometrically, which is why mixing up the two costs marks in exam answers.

Three terms describe linear motion:

Speed: The distance covered per unit of time. It's a scalar quantity, meaning it has no direction.
Velocity: The rate of change of displacement (distance in a specific direction) over time. It's a vector quantity, meaning it includes both magnitude and direction.
Acceleration: The rate of change of velocity over time. It can be positive (speeding up) or negative (slowing down).

Example

A sprinter running 100 meters in 10 seconds has a speed of 10 m/s.
If they start from rest and reach this speed in 2 seconds, their acceleration is 5 m/s².

Position and measurement describe where motion occurs

Definition

Position

Position refers to the location of an object or body, typically given by its coordinates.

Definition

Coordinates

Coordinates measure distance from an origin (e.g., in meters) and are given in two dimensions (x, y: horizontal and vertical) or three dimensions (x, y, z: horizontal, vertical, lateral). Two systems for three-dimensional coordinates: System 1: x = horizontal, y = vertical, z = lateral and System 2: x = horizontal, y = lateral, z = vertical. Angular coordinates are measured as angles around one or more axes.

Newton's laws of motion and linear motion

1. Newton's first law: the law of inertia

Definition

Newton's First Law

An object will remain at rest or keep moving at a constant velocity unless acted upon by an outside force. This law is also known as the law of inertia

This law emphasizes that a force is necessary to change the motion of an object.
This law explains why it is harder to start or stop an object's motion.
The resistance to change in motion is called inertia.

Definition

Inertia

Inertia is a property of matter that causes an object to resist changes in its state of motion. The more mass an object has, the greater its inertia.

Example

A soccer ball will not move unless kicked (object at rest) and will continue to roll in a straight line unless acted upon by external forces like friction or a player kicking it again (object in motion).
A hockey puck glides across the ice until friction or a player's stick changes its motion.

Inertia affects starts and stops in sport

Inertia explains the challenge faced by athletes when starting and stopping motion.
It takes significant force to overcome inertia and accelerate a stationary object or decelerate a moving object.

Example

Running: A sprinter at the starting line has to apply force to overcome inertia and accelerate from rest. The sprinter’s body tends to stay at rest until sufficient force is applied.
Football: A football, once kicked, continues in motion until external forces (e.g., friction with the ground, air resistance) slow it down or stop it.
Stopping: It takes more effort to stop a larger object (like a heavy sled) compared to a smaller one because of inertia.

Note

This law explains why athletes need to exert more force to overcome inertia when starting or stopping movement.

2. Newton's second law: the law of acceleration

Definition

Newton's Second Law

The force on an object is equal to its mass times its acceleration. This law states that the greater the force applied to an object, the greater the acceleration.

The acceleration of an object is proportional to the force applied and inversely proportional to its mass.

This is expressed as: F = ma

Where:

F is the force acting on the object (measured in Newtons, N),
m is the mass of the object (measured in kilograms, kg),
a is the acceleration of the object (measured in meters per second squared, m/s²).

Tip

This law shows how the force applied to an object influences its motion.
The greater the force applied to an object, the greater its acceleration, provided that the mass remains constant.

Common Mistake

Students often think more force always means more speed.
Remember - the object's mass matters!
A heavy shot put needs much more force than a tennis ball for the same acceleration.

Note

Acceleration is change in velocity demanded by the time taken.
So Newton's second law of motion could be rewritten as:
$$F = \frac{m(v - u)}{t}$$

Newton's second law explains acceleration in sport

To maximize acceleration, athletes aim to increase the force they apply and/or reduce their mass.
For example, a sprinter can strengthen the legs to increase force applied to the ground or reduce body fat to lower body mass.

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Note

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Tip

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Definition

Kinematics

Definition

Motion

Motion can be:

Linear (motion in a straight line), such as a sprinter running down a track.
Curvilinear (motion along a curved path), such as a football being kicked in a long arc.
Angular or rotational (motion around an axis), such as a figure skater spinning on one foot.
General (a combination of linear and angular motion), such as a cyclist pedaling while moving forward.

Definition

Linear Motion

Linear motion refers to movement along a straight path.

Vectors and Scalars

A scalar has size only, such as distance, speed, mass, and time.
A vector has both size and direction, such as displacement, velocity, acceleration, force, momentum, and impulse.
Vectors with the same direction add simply, while vectors in different directions must be combined geometrically, which is why mixing up the two costs marks in exam answers.

Three terms describe linear motion:

Speed: The distance covered per unit of time. It's a scalar quantity, meaning it has no direction.
Velocity: The rate of change of displacement (distance in a specific direction) over time. It's a vector quantity, meaning it includes both magnitude and direction.
Acceleration: The rate of change of velocity over time. It can be positive (speeding up) or negative (slowing down).

Example

A sprinter running 100 meters in 10 seconds has a speed of 10 m/s.
If they start from rest and reach this speed in 2 seconds, their acceleration is 5 m/s².

Position and measurement describe where motion occurs

Definition

Position

Position refers to the location of an object or body, typically given by its coordinates.

Definition

Coordinates

Newton's laws of motion and linear motion

1. Newton's first law: the law of inertia

Definition

Newton's First Law

An object will remain at rest or keep moving at a constant velocity unless acted upon by an outside force. This law is also known as the law of inertia

This law emphasizes that a force is necessary to change the motion of an object.
This law explains why it is harder to start or stop an object's motion.
The resistance to change in motion is called inertia.

Definition

Inertia

Inertia is a property of matter that causes an object to resist changes in its state of motion. The more mass an object has, the greater its inertia.

Example

A soccer ball will not move unless kicked (object at rest) and will continue to roll in a straight line unless acted upon by external forces like friction or a player kicking it again (object in motion).
A hockey puck glides across the ice until friction or a player's stick changes its motion.

Inertia affects starts and stops in sport

Inertia explains the challenge faced by athletes when starting and stopping motion.
It takes significant force to overcome inertia and accelerate a stationary object or decelerate a moving object.

Example

Running: A sprinter at the starting line has to apply force to overcome inertia and accelerate from rest. The sprinter’s body tends to stay at rest until sufficient force is applied.
Football: A football, once kicked, continues in motion until external forces (e.g., friction with the ground, air resistance) slow it down or stop it.
Stopping: It takes more effort to stop a larger object (like a heavy sled) compared to a smaller one because of inertia.

Note

This law explains why athletes need to exert more force to overcome inertia when starting or stopping movement.

2. Newton's second law: the law of acceleration

Definition

Newton's Second Law

The force on an object is equal to its mass times its acceleration. This law states that the greater the force applied to an object, the greater the acceleration.

The acceleration of an object is proportional to the force applied and inversely proportional to its mass.

This is expressed as: F = ma

Where:

F is the force acting on the object (measured in Newtons, N),
m is the mass of the object (measured in kilograms, kg),
a is the acceleration of the object (measured in meters per second squared, m/s²).

Tip

This law shows how the force applied to an object influences its motion.
The greater the force applied to an object, the greater its acceleration, provided that the mass remains constant.

Common Mistake

Students often think more force always means more speed.
Remember - the object's mass matters!
A heavy shot put needs much more force than a tennis ball for the same acceleration.

Note

Acceleration is change in velocity demanded by the time taken.
So Newton's second law of motion could be rewritten as:
$$F = \frac{m(v - u)}{t}$$

Newton's second law explains acceleration in sport

To maximize acceleration, athletes aim to increase the force they apply and/or reduce their mass.
For example, a sprinter can strengthen the legs to increase force applied to the ground or reduce body fat to lower body mass.

Definition

Paywall

(on a website) an arrangement whereby access is restricted to users who have paid to subscribe to the site.

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Note

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam quis nostrud exercitation.

Excepteur sint occaecat cupidatat non proident

Tip

Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
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A.1 Communication3 subtopics

A.2 Hydration and nutrition3 subtopics

A.3 Response3 subtopics

B.1 Generating movement in the body4 subtopics

B.2 Forces, motion and movement3 subtopics

B.3 Injury2 subtopics

C.1 Individual differences2 subtopics

C.2 Motor learning2 subtopics

C.3 Motivation3 subtopics

C.4 Stress and coping2 subtopics

C.5 Psychological skills2 subtopics

IB Sports, exercise and health science B.2.1.1 Linear Motion and Linear Kinematics in Sport Notes

A.1 Communication3 subtopics

A.2 Hydration and nutrition3 subtopics

A.3 Response3 subtopics

B.1 Generating movement in the body4 subtopics

B.2 Forces, motion and movement3 subtopics

B.3 Injury2 subtopics

C.1 Individual differences2 subtopics

C.2 Motor learning2 subtopics

C.3 Motivation3 subtopics

C.4 Stress and coping2 subtopics

C.5 Psychological skills2 subtopics

Vectors and Scalars

Position and measurement describe where motion occurs

Newton's laws of motion and linear motion

1. Newton's first law: the law of inertia

Inertia affects starts and stops in sport

2. Newton's second law: the law of acceleration

Newton's second law explains acceleration in sport

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account

Vectors and Scalars

Position and measurement describe where motion occurs

Newton's laws of motion and linear motion

1. Newton's first law: the law of inertia

Inertia affects starts and stops in sport

2. Newton's second law: the law of acceleration

Newton's second law explains acceleration in sport

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account