Describe how to find the center of gravity of a uniform wooden bar, including a diagram and method.

Here's how to determine the center of gravity of a uniform wooden bar:

STATION 1: Determination of the center of gravity of a wooden bar

Diagram (2 marks)
A diagram showing a uniform wooden bar balanced on a triangular prism. The balancing point should be indicated.

\begin{tikzpicture}[scale=0.8] % Wooden bar \draw[line width=2pt, brown!70!black] (-5,0) -- (5,0); \node[above] at (0,0.2) {Wooden Bar (100 cm long)}; \node[below] at (-5,0) {0 cm}; \node[below] at (5,0) {100 cm}; % Triangular prism (fulcrum) \draw[fill=gray!30] (-0.5,-0.5) -- (0.5,-0.5) -- (0,0) -- cycle; \node[below] at (0,-0.5) {Triangular Prism}; % Center of Gravity indication \draw[dashed] (0,0) -- (0,1); \node[above] at (0,1) {Center of Gravity (50 cm mark)}; \end{tikzpicture}

Method/Precaution (4 marks)

• Method:

  1. Place the uniform wooden bar horizontally on the triangular wooden prism.
  2. Carefully adjust the position of the triangular prism along the length of the bar until the bar is perfectly balanced and remains horizontal without tilting to either side.
  3. Once the bar is balanced, use the metre rule to read the mark on the wooden bar that is directly above the pivot point of the triangular prism. This mark indicates the position of the center of gravity.
  4. For a uniform bar, this point should be at its geometric center.

• Precaution:

  • Ensure the wooden bar is clean and free from any external weights or irregularities that might affect its balance.
  • Perform the experiment in a draft-free environment to prevent air currents from affecting the balance of the bar.
  • Ensure the triangular prism is stable and provides a sharp pivot point for accurate balancing.

Observation (2 marks)

• The wooden bar will balance horizontally when the triangular prism is placed exactly at the $50 \text{ cm}$ mark of the bar.
• If the prism is moved slightly from this point, the bar will tilt.

Inference/Conclusion (2 marks)

• The point at which the uniform wooden bar balances is its center of gravity.
• For a uniform bar, the center of gravity is located at its geometric midpoint, which for a $100 \text{ cm}$ bar is at the $50 \text{ cm}$ mark.