Motion

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Motion

Every day you see movement around you: the motorcycle moving down the avenue, the dog running in the park, or your own body as you walk to school or work.

According to physics, movement is the change in position of a body or object in a given time. For example: a duck was sleeping at eight in the morning, but five minutes later it started walking. It made a movement because it changed its position.

But it also moved when it lowered its head to drink some water, because its body changed position. This happened in seconds.

Now, if the object you are studying does not change position, it is said to be at rest, like a car that is stationary in the same place.

Once it starts rolling down the street, it will change its position because it will no longer be in the same place where it was parked, but in another place on the street. This change in position is called motion.

What is kinematics?

There are two branches that have focused on studying motion. One is kinematics, which allows you to understand its main characteristics through concepts such as displacement, velocity, acceleration, among others.

This discipline is responsible for describing motion in terms of trajectory and time variables, that is, motion in its simplest form.

On the other hand, there is dynamics, which determines the causes that generate motion, such as the forces that make objects move, and this is where Newton's Laws appear.

Types of Motion

Rectilineal motion: Describes a body with a linear trajectory and parallel velocity and acceleration.

Uniform circular motion: Describes a body moving around a rotational axis, with a constant radius and angular velocity, tracing a circumference. In this type of motion, bodies accelerate in the direction of the center of the circle.

Simple harmonic motion: Describes a periodic motion, such as that of a pendulum or an electromagnetic wave (light, for example). Mathematically, it is described in time by a harmonic function (sine or cosine). The motion may not be harmonic, that is, not repeat itself over time, but may still describe wave-like trajectories, in which case it is called wave motion.

Parabolic motion: Describes a motion that traces a parabola. It is the result of the composition of a uniform horizontal rectilinear movement and a uniformly accelerated vertical movement. An example of this type of motion is that of a ball thrown upward at an angle to the horizontal.

Elements of Motion

Trajectory: It is the line that can be used to describe the motion of a point body and that, depending on its nature, can be: rectilinear, curvilinear, circular, elliptical, or parabolic.

Speed: It is the relationship between the distance traveled and the time it takes the object to travel (the greater the speed, the greater the distance per unit of time a body travels).

Acceleration: It is the change in speed (final speed minus initial speed) per unit of time.

Examples of Motion

The clocks of yesteryear worked based on the motion of a pendulum to mark the seconds. This motion is the perfect example of the simple pendulum motion, which is the same motion we use in movies to "hypnotize" someone.

Since the floor of bowling alleys is waxed to greatly reduce friction, the balls tend to move in a uniform, straight-line motion until they hit the pins.

To better understand motion, it is necessary to know the differences between velocity, speed, and acceleration

Velocity, Speed, and Acceleration

The concepts of speed and velocity are often somewhat confused, so here we share a key characteristic that will help you differentiate them and use them correctly.

Speed

Speed is the combination of two things: the distance an object travels and the time it takes to travel that distance.

For example, a car that is stopped is at rest. But as it starts traveling down the road, its speed begins to increase, and the faster it goes, the less time it will take to travel a certain distance.

This is why the measurement kilometers per hour is often used to refer to the speed of a means of transportation.

Velocity

Like speed, velocity takes into account the distance an object travels and the time it takes to travel that distance. It also includes the direction in which the object is moving .

For example, when an airplane travels 800 kilometers in one hour, we talk about speed. However, if you add to that description the fact that the airplane is heading south, you start talking about velocity.

In summary, for speed to exist, you must identify three concepts: Distance, Time, and Direction. In this example, we have:

Keep in mind that speed is a vector magnitude represented by arrows, which indicate the direction and sense of motion of a body. It can be linear, circular, curvilinear, parabolic, among others.

Acceleration

Acceleration refers to the variations in an object's speed with respect to time.

Let's take a Formula 1 car as an example, which must compete for approximately an hour and a half. During this time, it will not maintain the same speed, but will have to vary it according to its needs.

On curves, the driver will slow down for safety reasons and also decelerate when he needs to get to his station for maintenance. But once he gets back on track, he will increase his speed to make up for lost time. All of these speed variations are part of acceleration.

Examples from everyday life:

In the first one, there's an airplane moving at 850 km/h. This refers to speed, but if you say the airplane is traveling from the United States to Argentina, you're starting to refer to velocity.

In the second one, there's a space rocket going very fast, but if you also say it's going at a 42-degree angle to planet X, you're no longer talking about how fast it is, but rather how fast it's traveling.

In the third one, a turtle appears. It's no secret that turtles are slow, since they travel short distances in a long time. However, when you say the turtle is walking east of the yard to get its food, you're not talking about how fast it is, but rather that its speed is low.

Activity. Answer the following questions.

Remember to review the answers to the open-ended questions at the bottom of this page.

1. What does kinematics study?

2. Which of the following is an example of uniform circular motion?

3. What does simple harmonic motion describe?

4. What is motion?

5. What is the main difference between speed and velocity?

Once you click this button, the questions will close and you won't be able to change your answer.

6. What elements must be considered when calculating the speed of an object?

7. What is the difference between trajectory and distance?

8. What does acceleration refer to?

9. Name the 4 elements of motion.

10. Speed is the mixture...

Still have questions?

We recommend visiting the following material for greater knowledge or understanding of the topic:

Answers to open questions:

6. The distance the object travels, the time it takes to travel that distance, and the direction in which it is moving.

7. The trajectory is the line that a body describes as it moves, and it can be straight, curved, circular, etc. Distance is the total amount of space the body travels, regardless of its direction.

Motion

What is kinematics?

Types of Motion

Elements of Motion

Examples of Motion

Velocity, Speed, and Acceleration

Speed ​​

Velocity ​​

Acceleration

Examples from everyday life:

Activity. Answer the following questions.

1. What does kinematics study?

2. Which of the following is an example of uniform circular motion?

3. What does simple harmonic motion describe?

4. What is motion?

5. What is the main difference between speed and velocity?

6. What elements must be considered when calculating the speed of an object?

7. What is the difference between trajectory and distance?

8. What does acceleration refer to?

9. Name the 4 elements of motion.

10. Speed ​​is the mixture...

Still have questions?

Answers to open questions:

Speed

Velocity

10. Speed is the mixture...