A metal bar `70 cm` long and `4.00 kg` in mass is supported on two knife edges placed `10 cm` from each end. A `6.00 kg` weight is suspended at `30 cm` from one end. Find the reactions at the knife edges. Assume the bar to be of uniform cross-section and homogeneous.

Explanation

To solve the problem, we need to find the reactions at the knife edges (N1 and N2) when a metal bar is supported at two points with an additional weight suspended from it. Here’s a step-by-step solution:

### Step 1: Understand the System
- The metal bar is 70 cm long and has a mass of 4.00 kg.
- The bar's weight (W_bar) can be calculated using the formula:
\[ W_{\text{bar}} = \text{mass} \times g = 4.00 \, \text{kg} \times 9.81 \, \text{m/s}^2 = 39.24 \, \text{N} \]
- The knife edges are placed 10 cm from each end, meaning they are located at 10 cm and 60 cm along the length of the bar.
- A 6.00 kg weight (W_weight) is suspended at 30 cm from one end, which can be calculated as:
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