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Fundamentals of Motion
Fundamentals of Motion
Objectives
Define what is motion
Discuss the concept of motion in other scientific domains.
Solve problems involving motion, such as distance, displacement, speed, and velocity.
What is motion?
What is motion?
Motion is fundamental concept in physics that helps us understand how object change their positions relative to other objects or reference points.
A reference points is any point in space that we use to compare or measure the position and motion of other things.
The origin (0,0) is usually the reference point within a Cartesian Coordinate System. This system is divided into four distinct quadrants, denoted as I,II,III, and IV. These quadrants delineate the positioning of both x- and y-values, its is the quadrants boundaries.
It also introduce as the four cardinal directions-north (N), south (S), east (E), and west (W), as fundamental conventions utilized in cartesian plane.
Real life Example:
Real life Example:
Imagine you're waiting for a e-jeep at a waiting shed, and you're looking at the e-jeep as it approaches. In this example, the motion of the e-jeep is what we’re observing—how its position changes over time.
Explanation:
Reference Point: The waiting shed is your reference point. You use this fixed point to observe the motion of the e-jeep. While you are standing still at the waiting shed, the e-jeep is changing its position as it moves toward you.
As the e-jeep moves closer to the waiting shed, you can say that its position is changing relative to the waiting shed. For example, at first, it might be 100 meters away, but then after a few minutes, it is only 10 meters away.
How It Works:
Reference Point: You use the waiting shed as the fixed point to compare the position of the e-jeep.
Motion: The e-jeep is in motion because its position is changing over time, moving from a far distance to closer to you.
In this case, the motion is the change in the e-jeep's position relative to the reference point (the waiting shed). Without a reference point, we wouldn’t be able to describe the motion or the position of the e-jeep accurately.
What is distance and displacement?
What is distance and displacement?
Distance (d) denotes the length of the path taken by a moving object. Displacement (d or Δd) is the shortest span between the final and initial and final positions. Delta (Δ) means “change”. It is the difference between the final and initial values of any physical quantity.
The fundamental unit of length in the International System of Units (SI) is the meter (m), which serves as a standard for measuring both distance and displacement.
Notes: Displacement symbol has an arrow above the "d or Δd"
Sample Problem for Distance and Displacement
Sample Problem for Distance and Displacement
Statement:
"You walk in one direction and then turn around and walk back the same way. What is your distance and displacement?"
Answer: Your distance is the total path you walked. Your displacement is zero because you ended up where you started.
Real Life Example
Real Life Example
Scenario:
Imagine you walk from your home to the school. Along the way, you might take a few turns or follow a curved path. Now, let’s look at how distance and displacement differ:
Distance (d)
Distance refers to how far you travel along the path you took. It doesn't matter if you take a curvy or straight path.
For example, let’s say the path you walked was 2 km long (even if you walked around a few blocks or took some turns).
Displacement (Δd)
Displacement is the shortest straight-line distance from your starting point (home) to your ending point (the store). It doesn’t matter how much you curved your path—it’s just the straight-line distance.
If your home and the school are 1.4 km apart in a straight line, then your displacement is 1.4 km.
Delta (Δ)
The symbol Δ (delta) means change. So, Δd means the change in distance or displacement.
In this case, Δd is the difference between the starting position (your home) and the final position (the store).
Speed
Speed
Speed (v), a scalar quantity, is defined as the distance (d) traveled divided by time (t).
The standard unit of speed in the International System of Units (SI) is meters per second (m/s). Other common units include kilometers per hour (km/h) and miles per hour (mph)
Velocity
Velocity
Velocity is a fundamental concept in physics that describes the rate at which an object changes its position in a specific direction. Unlike speed, which is a scalar quantity that only considers how fast an object is moving, velocity is a vector quantity that incorporates both magnitude (speed) and direction.
Velocity (v), a vector quantity, is the displacement (d or Δd) over time (t). The speed in a particular direction is also called velocity.
Sample Problem for Speed and Velocity
Statement:
"If you run in a straight line and then turn around and run in the opposite direction at the same speed, how does your speed and velocity change?"
Answer: Your speed stays the same, but your velocity changes because the direction you’re moving in has changed.
Real Life Example about speed and velocity
Real Life Example about speed and velocity
Speed:
You’re riding your bike around the neighborhood. Someone asks, "How fast are you going?" You answer, "I’m going really fast." You only tell them how fast you're moving, not where you're going. This is speed — just how fast, no direction.
Velocity:
Now, someone asks, "Which way are you going?" You say, "I’m riding 10 blocks north." Now, you’re telling both how fast you're going and the direction you’re moving. This is velocity — both speed and direction.
Difference:
Speed: How fast you’re going, no direction.
Velocity: How fast and in which direction.
Notes: Given the SI units for length and time are meter (m) and second (s), respectively, it follows that we can express speed and velocity using the unit meter per second (m/s). Other common units of speed or velocity include feet per second (ft/s), kilometers per hour (km/h), and miles per hour (mi/h).
Average Speed
Average Speed
The average speed can be calculated by dividing the total distance (dT) traveled by the total elapsed time (tT).
Average Velocity
Average Velocity
Average velocity can be computed using the rate of change of the displacement. Average velocity can also be calculated if the initial and final velocities are given.
Average Speed and Average Velocity:
Statement:
"You travel in one direction for a certain distance and then travel the same distance in the opposite direction. What is your average speed and average velocity?"
Answer: Your average speed is the total distance divided by the total time, but your average velocity is zero because your displacement is zero (you returned to the starting point).
Real Life Example on Average Speed and Velocity
Real Life Example on Average Speed and Velocity
Scenario:
Sarah walks to school every day, which is 1 kilometer from her house. One day, she stops to chat with a friend, but still arrives at school after 15 minutes.
Average Speed:
Average Speed is the total distance Sarah traveled (1 km) divided by the total time (15 minutes). It shows how fast she was moving overall, even though she stopped.
Average Velocity:
Average Velocity takes direction into account. It looks at the straight-line distance from her house to the school and tells us how fast she changed position in that direction.
Summary:
Average Speed tells you how fast Sarah was moving in total.
Average Velocity also includes the direction of her movement.
This helps Sarah understand both how fast and in what direction she moved during her walk to school!
Uniform Motion
Uniform Motion
Uniform motion refers to the movement of an object at a constant speed in a straight line, meaning it covers equal distances in equal intervals of time. In uniform motion, the velocity remains constant, which means there is no acceleration acting on the object.
The only formula you need in solving a problem with uniform motion is;
Sample Problem for Uniform Motion
Sample Problem for Uniform Motion
Statement:
"A car moves at a constant speed on a straight road for a long period of time. Is its motion uniform?"
Answer: Yes, the motion is uniform because the car is moving at the same speed and in the same direction.
Note: If there are only three physical quantities, you can use the triangle technique to solve for the different unknowns.
Visual Representation of Motion
Visual Representation of Motion
Constant Velocity
Constant velocity describes the motion of an object that moves in a straight line at a steady speed without any changes in direction or speed over time.
Objects with a constant velocity have no acceleration
Uniformly increasing velocity
The velocity of a body in a uniformly accelerated motion increases by equal amounts in equal intervals of time. This also indicates that it moves at a constant acceleration.
Motion can be represented through graphs and becomes much clearer when you think "slope". Slope (m) means how much you go up or down (rise) compared to how much you go left or right (run).
A line's slope can be positive (sloping upward), negative (sloping downward), zero (horizontal), or undefined (vertical).
Let's Have a Game!
Let's Have a Game!
Other References
Other References
Checking For Understanding
Checking For Understanding
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