Projectile Motion Part 1| Grade 9 Science Quarter 4 Week 1 Lesson

Summary

In this video, the host introduces a lesson on the horizontal and vertical motions of a projectile for Grade 9 science students. The lesson revisits Newton's second law of motion and explores concepts like acceleration, gravity, and projectile motion. Through real-life examples and activities, students learn about uniformly accelerated motion and how horizontal and vertical motions operate independently in projectile motion. The video includes problem-solving exercises related to acceleration and velocity and concludes with shout-outs to the viewers. It encourages students to engage, subscribe, and stay tuned for the next lesson.

Takeaways

• 📚 The lesson focuses on understanding the horizontal and vertical motions of a projectile.
• 🔍 Newton's second law of motion is reviewed, stating that the net force on an object is equal to the mass of the object multiplied by its acceleration.
• 🚦 Traffic enforcers are used as an example to explain the concept of uniform acceleration and how it relates to speed limits on roads.
• 📈 Acceleration is defined as the rate of change of velocity with time, and it is a vector quantity with both magnitude and direction.
• 🚗 The script explains that most acceleration is non-uniform due to various factors such as traffic conditions.
• 📊 A table of speedometer readings is used to illustrate how to determine if a vehicle has uniform acceleration.
• 🌐 The script discusses gravity as the force that causes objects to fall towards the Earth, leading to uniformly accelerated motion in free-falling objects.
• 🏋️‍♂️ An example of a coin toss is used to explain the effect of gravity on vertical motion.
• 📉 The script differentiates between horizontal and vertical components of projectile motion, noting that horizontal motion has no acceleration while vertical motion is affected by gravity.
• 🎾 The trajectory of a projectile, such as a ball in a sport, is described as parabolic due to the influence of gravity.
• 📐 The lesson includes an example problem that demonstrates how to calculate the height of a table and the final velocity of a horizontally launched projectile.

Q & A

What is the second law of motion as described in the script?

The second law of motion, also known as the law of acceleration, states that the acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force in the same direction as the net force and inversely proportional to the mass of the object.

What is uniformly accelerated motion (UAM) and how does it relate to traffic enforcers?

Uniformly accelerated motion (UAM) is a type of motion where the velocity of an object changes by an equal amount in every equal time period, and the acceleration is constant. The script relates UAM to traffic enforcers by explaining that speed limits on roads prevent vehicles from accelerating unnecessarily, which is a form of controlled acceleration.

How is acceleration defined in the context of the script?

Acceleration is defined as the rate of change in velocity with time. It is a vector quantity having both magnitude and direction.

What is the acceleration due to gravity, and how does it affect free-falling objects?

The acceleration due to gravity is 9.8 meters per second squared, and it is a constant acceleration for all falling bodies regardless of their mass and weight. This means that all objects on Earth's surface are accelerated towards the center of the Earth at this rate, causing objects in free fall to exhibit uniformly accelerated motion.

What is projectile motion and how does it differ from other types of motion?

Projectile motion is a form of motion where an object moves in a curved path under the influence of gravity. It differs from other types of motion because it involves both horizontal and vertical components working independently, with the horizontal motion typically having no resistance and constant velocity, while the vertical motion is influenced by gravity, causing a change in velocity.

What are the characteristics of horizontal motion in projectile motion?

In projectile motion, horizontal motion is characterized by no resistance, a constant horizontal velocity (vx), zero horizontal acceleration (ax), and the horizontal distance covered is referred to as the range (dx).

What are the characteristics of vertical motion in projectile motion?

Vertical motion in projectile motion is characterized by the force of gravity acting on the object, a constant acceleration equal to negative 9.8 meters per second squared (ay), a non-constant vertical velocity (vy) due to the acceleration caused by gravity, and the vertical distance is referred to as the height (dy).

How is the trajectory of an angle-launch projectile described in the script?

The trajectory of an angle-launch projectile is described as a full parabolic motion, which is a curved path that the object follows due to the influence of gravity while moving horizontally.

What is the formula used to calculate the height of a table when given the horizontal distance and initial velocity of a horizontally launched projectile?

The formula used to calculate the height of a table in the script is: height = (1/2) * acceleration due to gravity * time^2. Time is determined by dividing the horizontal distance by the initial velocity.

How is the final velocity of a horizontally launched projectile calculated just before it hits the ground?

The final velocity of a horizontally launched projectile just before it hits the ground is calculated using the formula: final velocity = -sqrt(2 * acceleration due to gravity * height). The negative sign indicates the downward direction of the velocity.