Equations of Uniformly Accelerated Motion - 2.7 | 2. Motion in One Dimension | ICSE Class 9 Physics
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2.7 - Equations of Uniformly Accelerated Motion

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Interactive Audio Lesson

Listen to a student-teacher conversation explaining the topic in a relatable way.

Understanding Final Velocity Equation

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0:00
Teacher
Teacher

Today, we will start with the first equation of uniformly accelerated motion: v = u + at. Can anyone tell me what each symbol represents?

Student 1
Student 1

I think v is the final velocity, right?

Teacher
Teacher

Exactly! v is the final velocity. And u is the initial velocity. Now, who can tell me what a and t stand for?

Student 2
Student 2

a is acceleration and t is time!

Teacher
Teacher

Perfect! So this equation shows that the final velocity depends on the initial velocity, how fast the object is accelerating, and how long it has been accelerating. A good mnemonic to remember this is 'VUTAT' – final Velocity (v) equals Initial Velocity (u) plus Acceleration (a) times Time (t).

Student 3
Student 3

So if the acceleration is zero, would v always equal u?

Teacher
Teacher

Exactly! If there’s no acceleration, the object maintains a constant velocity.

Student 4
Student 4

Can we solve an example using this equation?

Teacher
Teacher

Of course! If an object has an initial velocity of 5 m/s, accelerates at 2 m/sΒ² for 3 seconds, what would the final velocity be? Let's calculate it together.

Teacher
Teacher

Using the formula v = 5 + 2*3, we find v = 5 + 6, thus v = 11 m/s.

Teacher
Teacher

In summary, the first equation relates final velocity to initial velocity, acceleration, and time. Stay tuned for the next equation!

Explaining the Displacement Equation

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0:00
Teacher
Teacher

Now let's move on to the second equation: s = ut + \frac{1}{2}at^2. Who can explain what s represents?

Student 1
Student 1

I think s is the displacement?

Teacher
Teacher

Correct! Displacement s tells us how far the object has moved. Now, can someone break down the equation for us?

Student 2
Student 2

The first part, ut, is the distance covered at constant initial velocity, and the second part, \frac{1}{2}at^2, is for the distance covered due to acceleration.

Teacher
Teacher

Exactly! This formula shows that displacement depends on both the initial velocity and the effect of acceleration over time. It's essential to realize that if acceleration is zero again, the second half disappears, and we fall back to s = ut.

Student 3
Student 3

Isn't there a way to think of the \frac{1}{2} at^2 term as half of something?

Teacher
Teacher

Yes! You can visualize that you're calculating the area under a velocity-time graph, which explains this half factor very well. Let's do a quick example for practice.

Student 4
Student 4

Okay! If I have u = 2 m/s, a = 3 m/sΒ², and time = 4 seconds, could we calculate s?

Teacher
Teacher

Absolutely! Plugging in the numbers gives s = 2*4 + \frac{1}{2}*3*(4^2) = 8 + \frac{1}{2}*3*16 = 8 + 24 = 32 m. Great job!

Teacher
Teacher

In summary, this equation shows how both uniform motion and accelerated motion contribute to the overall displacement.

Discussing the Velocity-Squared Equation

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0:00
Teacher
Teacher

Finally, let's look at the third equation: vΒ² = uΒ² + 2as. Who can explain why this equation is important?

Student 1
Student 1

It lets us find the final velocity without needing time.

Teacher
Teacher

Exactly! This equation is beneficial in situations where time isn't easily measurable. Let’s break it down: what does it highlight?

Student 2
Student 2

It relates initial and final velocities using displacement and acceleration.

Teacher
Teacher

Great job! So, if an object is moving and we want to find how fast it goes after covering a distance, this equation is our go-to solution. Can anyone tell me if it’s possible for u and a to be zero?

Student 3
Student 3

If both are zero, then v must also be zero, indicating the object isn't moving.

Teacher
Teacher

That's correct! Now let’s do an example. If u = 5 m/s, a = 2 m/sΒ², and we want to know v when s = 20m, what would we calculate?

Student 4
Student 4

We use the equation to find vΒ² = 5Β² + 2*2*20 = 25 + 80, so vΒ² = 105, and v = sqrt(105).

Teacher
Teacher

Exactly! This equation is powerful and links concepts cohesively. Remember, it’s important for predicting outcomes in motion. Let’s summarize: we covered the final velocity, displacement, and velocity-squared equations and their relationships.

Introduction & Overview

Read a summary of the section's main ideas. Choose from Basic, Medium, or Detailed.

Quick Overview

This section introduces the equations that describe motion along a straight line with constant acceleration, focusing on relationships between displacement, velocity, acceleration, and time.

Standard

The section covers three key equations used in uniformly accelerated motion, showcasing how initial velocity, final velocity, acceleration, displacement, and time relate. Each equation highlights a different aspect of motion, emphasizing systematic relationships crucial for understanding linear motion physics.

Detailed

Equations of Uniformly Accelerated Motion

When analyzing motion along a straight line with constant acceleration, three fundamental equations emerge:

  1. Final Velocity Equation:
    v = u + at
  2. This equation relates the final velocity (v) of an object to its initial velocity (u), the acceleration (a), and the time (t) during which the acceleration occurs.
  3. Displacement Equation:
    s = ut + \frac{1}{2}at^2
  4. This formula gives the displacement (s) of the object as a function of initial velocity, time, and acceleration, showing that displacement depends on both constant and changing motion.
  5. Velocity Squared Equation:
    v^2 = u^2 + 2as
  6. This equation connects initial velocity, final velocity, and displacement via acceleration without time, providing a useful alternative for solving motion problems.

These equations form the foundation for problems regarding uniformly accelerated motion in physics, allowing students to predict an object's future behavior under constant acceleration.

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Audio Book

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Introduction to Uniformly Accelerated Motion

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When motion is along a straight line with constant acceleration:

Detailed Explanation

Uniformly accelerated motion refers to the movement of an object where it experiences a consistent rate of acceleration. This means that the object's speed changes by the same amount in every unit of time. For instance, if an object accelerates at 2 meters per second squared, its speed increases by 2 meters per second every second. The key aspect here is that the acceleration remains constant, making it easier to predict the object's movement over time.

Examples & Analogies

Imagine a car increasing its speed as it moves down a straight road. If the car accelerates steadily, such as going from 0 to 60 km/h in 5 seconds, it does so uniformly. This steady increase in speed is an example of uniformly accelerated motion.

First Equation of Motion

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  1. v = u + at

Detailed Explanation

The first equation of motion describes the relationship between final velocity (v), initial velocity (u), acceleration (a), and time (t). It states that the final velocity of an object equals its initial velocity plus the product of acceleration and time. This equation is useful for calculating the final speed of an object when you know how much time it has been accelerating and the rate of acceleration.

Examples & Analogies

Consider a sprinter who starts a race with an initial speed (u) of 5 m/s and accelerates at 2 m/sΒ² for 3 seconds. To find out how fast they will be running after this acceleration, you can use this equation. In this case, the final speed would be 5 m/s + (2 m/sΒ² Γ— 3 s) = 11 m/s.

Second Equation of Motion

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  1. s = ut + 1/2 atΒ²

Detailed Explanation

The second equation of motion relates displacement (s) to initial velocity (u), time (t), and acceleration (a). It states that the displacement of an object is equal to its initial velocity times the time plus half of the acceleration times the square of the time. This equation helps determine how far an object has traveled during the time of acceleration.

Examples & Analogies

Imagine throwing a ball upward with an initial speed of 10 m/s. If it accelerates downward at 9.8 m/sΒ² due to gravity, and you want to know how high it goes after 2 seconds, you can use this equation. The height (s) can be calculated by: s = (10 m/s Γ— 2 s) + (1/2 Γ— -9.8 m/sΒ² Γ— (2 s)Β²) = 20 m - 19.6 m = 0.4 m.

Third Equation of Motion

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  1. vΒ² = uΒ² + 2as

Detailed Explanation

The third equation of motion connects the final velocity (v), initial velocity (u), acceleration (a), and displacement (s) without involving time. It states that the square of the final velocity equals the square of the initial velocity plus two times the acceleration multiplied by the displacement. This equation is particularly useful in cases where time is not known but the other variables are.

Examples & Analogies

Consider a skateboarder who starts from rest (initial velocity = 0) and accelerates down a ramp at 3 m/sΒ² for a distance of 15 meters. To find their final velocity at the bottom of the ramp, you can use this equation: vΒ² = 0Β² + 2(3 m/sΒ²)(15 m) = 90 mΒ²/sΒ², making the final velocity v = sqrt(90) β‰ˆ 9.49 m/s.

Definitions & Key Concepts

Learn essential terms and foundational ideas that form the basis of the topic.

Key Concepts

  • Final Velocity Equation: v = u + at, relates final velocity to initial velocity, acceleration, and time.

  • Displacement Equation: s = ut + \frac{1}{2}at^2, shows how both uniform and accelerated motion contribute to displacement.

  • Velocity-Squared Equation: vΒ² = uΒ² + 2as, connects velocity and displacement without needing time.

Examples & Real-Life Applications

See how the concepts apply in real-world scenarios to understand their practical implications.

Examples

    1. An object starts from rest (u=0) and accelerates at 3 m/sΒ² for 5 seconds. Find v and s.
    1. A car accelerates from 10 m/s with a constant acceleration of 4 m/sΒ² for 6 seconds. Calculate its final velocity and total displacement.

Memory Aids

Use mnemonics, acronyms, or visual cues to help remember key information more easily.

🎡 Rhymes Time

  • To find the velocity, just use v = u, add at in haste; time and speed will lead you straight, forward in the race!

πŸ“– Fascinating Stories

  • Imagine a car on a long road trip, starting carefully at a speed of u. As it speeds up with acceleration a, it journeys further with time t, discovering new distances along the way.

🧠 Other Memory Gems

  • Remember VUTAT for v = u + at, where V represents final velocity, U represents initial velocity, and T represents time.

🎯 Super Acronyms

DVA

  • Displacement
  • Velocity
  • Acceleration – keep these in mind when solving equations of motion.

Flash Cards

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Glossary of Terms

Review the Definitions for terms.

  • Term: Displacement

    Definition:

    The shortest distance from the initial to the final position of an object, having both magnitude and direction.

  • Term: Initial Velocity (u)

    Definition:

    The velocity of an object at the start of observation.

  • Term: Final Velocity (v)

    Definition:

    The velocity of an object at the end of a certain time period.

  • Term: Acceleration (a)

    Definition:

    The rate of change of velocity of an object.

  • Term: Time (t)

    Definition:

    The duration over which motion occurs.