O-Level Physics Visual Drawing Clinic

Static Electricity Pendulum

Dennis, this is not an algebra contest. This lesson turns the charged pith ball problem into a ruler-based connect-the-dots game with rules.

No calculator escape hatch Ruler only
charged plate + + + + + Weight Electric Force Tension
Rule 1: one dot first For an FBD, the ball becomes a central dot. All force arrows start from that dot.
Rule 2: ruler beats instinct Every vector is a straight measured line. No slanted freehand arrows, no curve-following arrows.
Rule 3: no calculator The question says draw to determine, so the answer must come from the drawing.

Mindset Reset

Before touching the ruler

Dennis, drawing is just a connect-the-dots game with rules. Your algebra brain is powerful, but today it has to sit in the passenger seat. Do not use your calculator to escape the visual task.

  1. Translate the story into directions. A charged pith ball hangs on a string and is repelled horizontally by a charged plate. That means one vertical force, one horizontal force, and one diagonal force.
  2. Commit to the drawing command. If the question says "draw to determine", formulas are not the method. The ruler is the method.
  3. Use the central dot as your anchor. When your brain freezes, place one dot at the ball's centre. The dot tells every force where to begin.

FBD Step-By-Step

All arrows start at the dot

The 3-Force Rule for a hanging charged ball: Weight is strictly down, Electric Force is strictly horizontal away from the plate, and Tension points diagonally along the string toward the support.

Weight Electric Force Tension Pass test: 3 arrows, 1 origin, clean directions.
  1. Draw one central dot. This dot represents the pith ball's centre of mass. Do not draw arrows from the string, plate, or surface.
  2. Draw Weight straight down. Use a ruler. The arrow must be vertical and labelled Weight or W.
  3. Draw Electric Force horizontally. The plate repels the charged ball, so the force is horizontal away from the plate. It does not slope.
  4. Draw Tension up-left. Tension follows the string back toward the support. It starts at the same central dot.
Image Generation Prompt: Correct FBD 
Create a clean O-Level Physics free body diagram for a charged pith ball suspended by a string near a charged plate. Use a plain white background. Show only one central black dot representing the ball's centre of mass. Draw exactly three straight arrows, and make sure all three arrows originate from the central dot: a strictly downward red arrow labelled "Weight", a strictly horizontal blue arrow pointing right labelled "Electric Force", and a diagonal green arrow pointing up-left labelled "Tension". The diagram must look like a ruler-drawn exam diagram, with clear labels, no extra forces, no curved arrows, and no arrows starting from different points.

Vector Scale Diagram

Tip-to-tail, not tip-to-tip

NO CALCULATOR RULE: no Cosine Rule, no component calculation, no mental shortcut. Choose a scale, measure with a ruler, and let the triangle give the answer.

Weight Electric Force Resultant Tension closes triangle Scale example: 1 cm = 0.1 N. Measure lines, then convert.
  1. Choose a scale. Example: 1 cm = 0.1 N. Write the scale before drawing, so every line has meaning.
  2. Draw Weight downward first. Start from a clean point. Use a ruler and draw the vertical downward vector to scale.
  3. From the tip of Weight, draw Electric Force. Your second vector starts at the arrowhead of the first vector. This is the tip-to-tail rule.
  4. Connect the start to the final tip. This gives the Resultant. To show equilibrium, close the triangle with Tension in the opposite direction.
Image Generation Prompt: Closed Vector Triangle 
Create a clean O-Level Physics vector scale diagram for a static electricity pendulum problem. Use a plain white background with faint graph-paper grid lines. Show a closed vector triangle drawn with ruler-straight arrows. Step 1: a red vertical arrow labelled "Weight" points straight downward from the starting point. Step 2: from the tip/arrowhead of the Weight vector, a blue horizontal arrow labelled "Electric Force" points right. Step 3: connect the original starting point to the final tip of the Electric Force vector with a black arrow labelled "Resultant". Also show a green dashed arrow from the final tip back to the original starting point labelled "Tension closes triangle". Emphasize tip-to-tail construction, measured straight lines, clear arrowheads, and no calculator/formula symbols.

Red-Line Checks

Exam discipline

Before Dennis submits the drawing, he should inspect it like a marker with a red pen. The goal is not artistic beauty; the goal is zero convention penalties.