GCSE Physics - Resultant Forces & Free Body Diagrams #42

Summary

This video tutorial explains the concept of free body diagrams, which are simple illustrations showing all forces acting on an object. It uses the example of an airplane to demonstrate how to calculate the resultant force by considering thrust, drag, weight, and lift. The video illustrates how to break down the forces into horizontal and vertical components and find the net force, highlighting the importance of equilibrium when forces cancel each other out.

Takeaways

• 📚 Free body diagrams are simple illustrations that depict all forces acting on a specific object using force arrows.
• 🚀 An example given in the script is a plane in flight, which has forces like thrust, drag, weight, and lift represented by arrows with magnitudes and directions.
• 🔍 The magnitude of force is indicated by the length of the arrows, and can be labeled in units such as newtons for precision.
• ⚖️ Forces acting in different directions can cancel each other out, leading to a resultant force that represents the overall force on the object.
• 📏 Calculating the resultant force is often done by considering horizontal and vertical components separately.
• 🔄 For the vertical component in the plane example, forces of equal magnitude but opposite direction cancel, resulting in zero net force.
• 🔄 In the horizontal component, the resultant force is calculated by subtracting the opposing forces, resulting in a net force to the right in the given example.
• ⚖️ If opposing forces are equal, such as 120,000 newtons each way, the resultant force in that direction is zero, indicating equilibrium.
• 🧩 When all components are in balance, the object is in equilibrium, with no resultant force acting on it.
• 🔍 Understanding resultant forces is crucial for analyzing the dynamics of objects in various scenarios, including flight.
• 👋 The video concludes by emphasizing the usefulness of free body diagrams in determining the overall effect of forces on an object.

Q & A

What is the main topic of the video?

The main topic of the video is the use of free body diagrams to find the resultant force on an object.

What are free body diagrams?

Free body diagrams are simple diagrams that show all the forces acting on a particular object using force arrows.

How are forces represented in a free body diagram?

In a free body diagram, forces are represented by arrows, where the direction of the arrow indicates the direction of the force, and the length of the arrow can indicate the magnitude of the force.

What is the significance of labeling forces in newtons in a free body diagram?

Labeling forces in newtons provides a precise measure of the magnitude of the force acting on the object.

How can forces acting in different directions affect the resultant force?

Forces acting in different directions can cancel each other out to some extent, and the resultant force is what remains after considering these interactions.

What is the resultant force?

The resultant force is the overall force acting on an object, which can be found by considering the horizontal and vertical components separately and then combining them.

Why is it useful to consider the horizontal and vertical components of forces separately?

Considering the horizontal and vertical components separately simplifies the process of finding the resultant force, as it allows for the independent calculation of forces in each direction.

What is an example of how forces are calculated in the horizontal component of a free body diagram?

In the example given, there is a force of 120,000 newtons to the right and 90,000 newtons to the left. The resultant force in the horizontal direction is found by subtracting the leftward force from the rightward force, resulting in 30,000 newtons to the right.

What does it mean for an object to be in equilibrium?

An object is in equilibrium when there is no resultant force acting on it, meaning the forces acting in all directions are perfectly balanced.

How does the video illustrate the concept of equilibrium?

The video illustrates equilibrium by presenting a scenario where the air resistance is 120,000 newtons, which when subtracted from itself results in a horizontal resultant force of zero, indicating equilibrium.

What is the final message of the video?

The final message of the video is that it hopes the explanation of free body diagrams and resultant forces was useful for the viewers.

Outlines

00:00

📚 Introduction to Free Body Diagrams

This paragraph introduces the concept of free body diagrams, which are simple illustrations representing all the forces acting on a particular object using force arrows. The example of a plane flying through the sky is used to explain how different forces like thrust, air resistance (drag), weight, and lift are depicted with arrows indicating their direction and magnitude. The magnitude can be quantified in newtons, and the resultant force is found by considering the vector nature of forces and how they cancel each other out in different directions.

Keywords

💡Free Body Diagrams

Free body diagrams are simple illustrations that depict all the forces acting on a particular object. They are essential in physics for visualizing and analyzing the forces that influence an object's motion or state of rest. In the video, free body diagrams are used to represent the forces on a plane, such as thrust, drag, weight, and lift, which are crucial for understanding the resultant force acting on the plane.

💡Resultant Force

The resultant force is the single force that can be considered to act on an object, which is equivalent to the combined effect of all the individual forces acting on it. It is a vector quantity, meaning it has both magnitude and direction. In the context of the video, the resultant force is calculated by considering the horizontal and vertical components of the forces acting on the plane, such as thrust and drag, to determine the overall force influencing the plane's motion.

💡Force Arrows

Force arrows are graphical representations used in free body diagrams to indicate the magnitude and direction of the forces acting on an object. Each arrow's length corresponds to the force's magnitude, and its direction is shown by the arrowhead. In the video script, force arrows are used to represent the thrust, drag, weight, and lift forces on the plane, helping to visualize how these forces contribute to the resultant force.

💡Magnitude

Magnitude refers to the size or strength of a force, which is a scalar quantity. In the context of the video, the magnitude of a force is indicated by the length of the force arrows in the free body diagram. For example, the magnitude of the thrust and drag forces on the plane is represented by the length of their respective arrows, which helps in determining the resultant force.

💡Direction

Direction is a critical aspect of a force, as it defines the line along which the force is acting. In the video, the direction of forces is depicted by the orientation of the force arrows in the free body diagram. For instance, the thrust force is represented by an arrow pointing forward, indicating the direction of the force that propels the plane.

💡Vectors

Vectors are quantities that have both magnitude and direction, making them essential in physics for describing forces and motions. In the video, forces such as thrust, drag, weight, and lift are treated as vectors because they have specific directions and magnitudes that can be added or subtracted to find the resultant force on the plane.

💡Equilibrium

Equilibrium in physics refers to a state where the net or resultant force acting on an object is zero, meaning there is no change in the object's motion. In the video, an example is given where if the air resistance equals the thrust force, the horizontal resultant force would be zero, indicating that the plane is in a state of equilibrium.

💡Horizontal Component

The horizontal component of a force is the part of the force that acts along the horizontal axis. In the video, the horizontal component is considered when calculating the resultant force acting on the plane. For example, the thrust and drag forces are analyzed in the horizontal direction to determine if there is a net force causing the plane to move to the right or left.

💡Vertical Component

The vertical component of a force is the part of the force that acts along the vertical axis. In the video, the vertical components of the forces, such as lift and weight, are considered to determine if there is a net force causing the plane to move up or down. The script mentions that if the lift equals the weight, the vertical resultant force is zero.

💡Newtons

Newtons is the unit of measurement for force in the International System of Units (SI). It quantifies the magnitude of a force. In the video, the forces acting on the plane, such as thrust and drag, are labeled in newtons to provide a precise measure of their magnitude, which is essential for calculating the resultant force.

Highlights

Introduction to free body diagrams and their use in determining the resultant force on an object.

Explanation of free body diagrams as simple diagrams with force arrows representing the forces acting on an object.

Use of force arrows to represent different forces such as thrust, air resistance, weight, and lift.

Description of forces as vectors with both magnitude and direction.

Illustration of how the magnitude of force is indicated by the length of the arrows.

Labeling forces in newtons for precision.

Concept of forces canceling each other out to determine the resultant force.

Method of calculating resultant force by considering horizontal and vertical directions separately.

Example of a plane's free body diagram with forces in the vertical component balancing out to zero.

Calculation of the horizontal component's resultant force using the difference between opposing forces.

Resultant force of 30,000 newtons to the right in the given example.

Scenario where air resistance increases to 120,000 newtons, resulting in a horizontal resultant force of zero.

Discussion of equilibrium when horizontal and vertical forces are perfectly balanced with no resultant force.

Conclusion summarizing the video's content on free body diagrams and resultant forces.

Hopeful note for the viewers to find the video useful and an anticipation for the next video.

Transcripts

in today's video we're going to look at

three body diagrams

and how we can use them to find the

resultant force on an object

when we say free body diagrams all we

mean are simple diagrams that show all

the forces that are acting on a

particular object

we do this using force arrows

so if we took the example of a plane

flying through the sky

we will draw its free body diagram by

adding a bunch of different arrows that

represent all the forces acting on the

plane

so it would have one going forwards

which would be its thrust

one backwards for air resistance or drag

one downwards for its weight

and one upwards for its lift

because all forces are vectors

each of these has to have both a

magnitude and a direction

we can see the direction from which way

the arrows are pointing

but the magnitude of the force comes

from how long each of the arrows are

and to be more precise we can label each

of them in newtons

now because all these forces are acting

in different directions

some of them are going to cancel each

other out and once you've taken that

into account

what we'd have left is the resultant

force

which you can describe as the overall

force on an object

it's normally easiest to do this by

looking at the horizontal and vertical

directions separately

and calculating the overall size and

direction of the resultant force in each

case

for example the vertical component of

this free body diagram

involves a force of 80 000 newtons up

and 80 000 newtons down

so when we subtract one from the other

we're left with zero nutrients overall

for the vertical component

for the horizontal component though we

have 120 000 newtons to the right

and only 90 000 newtons to the left

so by doing right minus left

we get a resultant force of 30 000

newtons in the right direction

so overall

taking into account the vertical and

horizontal components

would still have an overall resultant

force of 30 000 newtons to the right

if though we had a slightly different

scenario where the air resistance was

120 000 newtons instead then we'd be

doing 120 000

minus 120 000

and so the horizontal resultant force

would be zero

now both the horizontal and vertical

components will be perfectly balanced

and so we would say that the object is

in equilibrium

because there's no resultant force

acting on it

anyway that's everything for this video

so hope you found it useful and we'll

see you soon