Motion, Forces, and Energy Revision - IGCSE 0625 Physics

Physical Quantities and Measurement Techniques

Measuring Devices

• Length: Measured using a ruler (not Vernier caliper or screw gauge).
• Volume: Measured using a measuring cylinder.
• Time Intervals: Measured using clocks and digital timers.

Measuring Volume Methods

• Irregular Shaped Objects: Use a measuring cylinder.
  • Steps:
    1. Measure initial volume of liquid (V1).
    2. Immerse object and measure new volume (V2).
    3. Volume of object = V2 - V1.
• Regular Shaped Objects: Use formula.
  • Example: Cuboid with length (L), breadth (B), and height (H).
    • Volume = L × B × H.

Determine Average Value from Multiple Readings

• Example: Thickness of a single page in a stack.
  • Formula: Total Thickness (X) / Number of Pages (Y).
  • Always place total value in the numerator and number in the denominator.

Measuring Time Period of a Simple Pendulum

• Simple Pendulum: Bob attached to a thread connected to a fixed end.
  • Time Period (T): Time taken for one complete oscillation.
    • Measure time for multiple oscillations, then calculate average.
  • Formula: T = Total Time taken / Number of Oscillations.
    • Example: If 10 oscillations take 5 seconds, T = 5/10 = 0.5 seconds.

Scalar and Vector Quantities

• Scalar Quantities: Have only magnitude (e.g., temperature, time, mass, energy).
• Vector Quantities: Have both magnitude and direction (e.g., force, weight, velocity).

Examples

• Scalar: Speed, time, mass, energy, temperature.
• Vector: Force, weight, velocity, acceleration, momentum, electric field strength, gravitational field strength.

Resultant of Two Vectors

• By Calculation: Use Pythagoras Theorem for right-angle vectors.

  • Steps:
    1. Redraw vectors using head-tail method.
    2. Use Pythagoras Theorem: Hypotenuse = √(base² + height²).
    3. Find angle using tan θ = opposite/adjacent.

• Example: 30N (right) and 20N (down).

  • Resultant = √(30² + 20²) = 36N.
  • Angle θ = tan⁻¹(20/30).

• Graphically (Scale Drawing): Draw exact measurements and directions.

  • Scale Example: 10N = 2 cm.
  • Draw vectors (e.g., 30N = 6 cm, 20N = 4 cm).
  • Measure resultant and angle with a protractor.
  • Convert back using the scale.

Summary

• Use calculation method for accurate and time-efficient results.
• Scale method for visual and precise graphical representation.