Remoulding (Leaving Cert Mathematics): Revision Notes
Remoulding
What is Remoulding?
Remoulding refers to the process of reshaping or reforming a solid object into a new shape without altering its material. This concept is commonly used in geometry problems where a solid is melted or reshaped, and the total volume remains constant.
Key Principles of Remoulding
Volume Conservation:
The volume of the original object equals the volume of the remoulded object.
Shapes May Change, but the Material Stays the Same:
The remoulded object may have a different surface area or dimensions, but the volume remains constant.
Common Scenarios:
- Melting a solid to form another shape (e.g., melting a sphere into a cylinder).
- Cutting a shape and rearranging it into another form.
Worked Examples
Example 1: Cylinder to Sphere
Problem: A cylindrical block of wax with a radius of 5 cm and height 12 cm is melted to form a sphere.
Find the radius of the sphere.
Solution:
Step 1: Calculate the volume of the cylinder:
Step 2: Equate to the volume of the sphere:
Step 3: Solve for :
Answer: The radius of the sphere is approximately 6.13 cm
Example 2: Cube to Cylinder
Problem: A cube with a side length of 10 cm is remoulded into a cylinder with a height of 15 cm.
Find the radius of the cylinder.
Solution:
Step 1: Calculate the volume of the cube:
Step 2: Equate to the volume of the cylinder:
Step 3: Solve for :
Answer: The radius of the cylinder is approximately 4.61 cm
Summary
- Remoulding Principle: The volume of the original and remoulded shapes is always equal.
- Volume Conservation Formula:
- Common applications involve transitioning between spheres, cylinders, cubes, and other shapes.
- Use the specific volume formula for each shape to solve remoulding problems.
- Practice with various geometrical shapes to enhance problem-solving skills.