Revision, Doubt and Practice Session (RDP -1)

Revision: Motion Blocks Overview

1. Introduction to Scratch & Basic Motion Blocks 

• Move Block: This block helps to move the sprite in steps in X-axis. (positive numbers → right direction, negative numbers → left direction).
  • Try It: Drag a Move [10] Steps block and click it. Change the value to -10 to move left.
• Turn Block: This block helps to rotate the sprites clockwise or counterclockwise.
  • Understanding Angles: The turn block rotates a sprite based on degrees:
    • Turn Right (Clockwise): A positive angle moves the sprite to the right (e.g., 90° turns it to the right side).
    • Turn Left (Counterclockwise): A negative angle moves the sprite to the left (e.g., -90° turns it to the left side).
    • Full Rotation: A 360° turn brings the sprite back to its original position.
  • Try It: Use Turn Right [15] Degrees and Turn Left [45] Degrees to rotate the sprite.
• Go to Random Position Block: This block helps to teleport the sprite to a random position on the stage.
  • Try It: Drag this block and click it multiple times to see the sprite jump around.

2. Understanding Coordinates & Advanced Motion Blocks 

• X-Y Coordinate System:
  • X-axis: It controls left-right movement (-240 to 240).
  • Y-axis: It controls up-down movement (-180 to 180).
  • (0,0) is the center of the stage, the origin.
  • Try It: Move the sprite to X: 100, Y: 50 manually and observe.
• Go to X-Y Block: Moves the sprite instantly to a specified location.
  • Try It: Set Go to X: 50, Y: -100 and run the script.
• Glide Block: Moves the sprite smoothly over time to a specific X-Y position.
  • Try It: Glide 2 secs to X: -100, Y: 100.

3. Motion Blocks Practice with an Animation 

• Forever Loop: This block helps to keep the animation running continuously.
  • Why use a Forever Loop?
    • Without it, actions in the program would happen only once and then stop.
    • With a Forever loop, the program can create continuous animations, movements, or repetitive behaviors, making interactions more dynamic and engaging.

Try It: Make a sprite bounce continuously across the screen.

• Steps:
  • Choose a ball sprite.
  • Add move 10 steps and if on edge, bounce inside a Forever loop.
  • Run the script and see the ball move endlessly.

Doubt Session

• Allow students to ask questions about any previous concepts.
• Discuss common mistakes (e.g., sprite not moving, incorrect X-Y values).
• Provide live debugging assistance for students facing issues with their Scratch projects.

Tricky Questions:

1. What happens if you set a sprite’s X value to 500 in Scratch? Will it be visible on the stage?

ANS: No, because the maximum X value visible on the stage is 240. Any value greater than that moves the sprite off-screen.

2. What will happen if you use both 'Go to X: 100 Y: 50' and 'Glide 2 secs to X: 100 Y: 50' back to back?

ANS: The sprite will instantly move to (100, 50) because of the Go to X-Y block and then try to glide to the same location, which means no visible movement.

3. How can you make a sprite move in a perfect circle using only Motion Blocks?

ANS: Use a combination of Glide blocks or small angle Turn blocks with a loop.

Example Script: This makes the sprite turn 360 degrees in small steps, forming a perfect circle.

Practice Project: Solar System Animation

Objective:

Create an animation where planets orbit around the sun using Set X-Y and Glide Blocks.

Steps to Create the Project:

1. Choose Sprites and Backdrop:

• Add a sun sprite at the center.
• Add three planet sprites (e.g., Earth, Mars(Use a ball sprite for this), Saturn).
• Choose a space-themed backdrop.
• Adjust the sizes and rename the sprites according to the project.
  
  Sun Size - 60
  Earth Size - 40
  Mars(Ball Sprite) - 50
  Saturn(Planet 2 Sprite) - 50

2. Set Initial Positions:

Each planet should start from a fixed position using Go to X-Y.

• Sun: Go to X: 0, Y: 0
• Planet 1 (Earth): Go to X: 150, Y: 50
• Planet 2 (Mars): Go to X: 100, Y: 0
• Planet 3 (Saturn): Go to X: 200, Y: -75

3. Create Orbital Motion Using Glide Blocks:

• Make each planet move around the sun in a circular path using Glide Blocks.
• Example for Earth:
  • Glide 2 secs to (0, 100)
  • Glide 2 secs to (-100, 0)
  • Glide 2 secs to (0, -100)
  • Glide 2 secs back to (150, 50)
• Repeat similar Glide Blocks for Mars and Saturn, adjusting their speeds to mimic real-world orbits.
•  Mars:
  • Glide 3 secs to (0, 100)
  • Glide 3 secs to (-100, 0)
  • Glide 3 secs to (0, -100)
  • Glide 3 secs back to (100, 0)
•  Saturn:
  • Glide 4 secs to (0, 100)
  • Glide 4 secs to (-100, 0)
  • Glide 4 secs to (0, -100)
  • Glide 4 secs back to (200, -75)

4. Use When Green Flag Clicked:

• Attach the movement script to When Green Flag Clicked to start the animation.

5. Use Rotate Block to make Sun rotate:

• Use a Rotate 5 deg block to turn the Sun.

6. Wrap in a Forever Loop:

Place all movement scripts inside a Forever Loop so the planets continuously orbit around the sun.

https://drive.google.com/file/d/1DLOKIuN6Gx8Xw8Xk3drBVAsZWU31F7EM/view?usp=sharing {Video Reference Link}