Link to original video by Teacher Apz

Science Grade 9 Projectile Motion: Horizontal and Vertical Motion

Short Summary:

This Grade 9 science lesson focuses on projectile motion, explaining the horizontal and vertical components of motion. The lesson reviews Newton's three laws of motion before diving into projectile motion, defining it as the movement of an object projected into the air. Key points include the constant horizontal velocity (unaffected by gravity) and the changing vertical velocity (affected by gravity). The lesson uses examples like dropping a bomb from a plane and kicking a football to illustrate the concepts and applies the principles to the Angry Birds game. The lesson emphasizes the parabolic trajectory of projectiles and provides formulas for calculating time of flight, horizontal distance, and maximum height. Students are assigned to create a video demonstrating projectile motion in two dimensions and its real-world applications.

Detailed Summary:

The lesson begins with a review of Newton's three laws of motion using a "guess the picture" game. The teacher explains each law with examples: inertia (objects resist changes in motion), F=ma (force equals mass times acceleration), and action-reaction (for every action, there's an equal and opposite reaction).

Next, the lesson introduces projectile motion, defining a projectile as any object projected and continuing to move due to its inertia. It emphasizes that projectile motion has two components: horizontal (constant velocity) and vertical (velocity changes due to gravity). The teacher explains that the horizontal velocity remains constant because gravity acts only vertically. The vertical velocity, however, changes; it decreases going up and increases going down. The combined effect creates a parabolic trajectory.

The lesson then differentiates between horizontally and vertically launched projectiles. Horizontally launched projectiles have zero initial vertical velocity, while vertically launched projectiles have an initial vertical velocity and an angle of launch that affects both horizontal and vertical components. Formulas for calculating horizontal and vertical components of velocity (using trigonometric functions) are introduced.

Two example problems are solved: one involving a bomb dropped from a plane (horizontally launched) and another involving a kicked football (launched at an angle). The teacher demonstrates how to use kinematic equations to calculate time of flight, horizontal distance, and maximum height for both scenarios. The Angry Birds game is used as a visual demonstration of projectile motion.

Finally, the lesson concludes with an assessment requiring students to answer questions and create a short video explaining projectile motion in two dimensions and its real-world relevance. The teacher states, "Horizontally launched projectiles have no upward trajectory...and it has no initial vertical velocity," highlighting a key distinction. The lesson also emphasizes the importance of understanding the different components and their impact on the projectile's path.