To determine the effort needed to lift a load using a machine, we first need to understand some key concepts: **Load**, **Effort**, **Velocity Ratio** (VR), and **Efficiency**.
1. **Load** is the force or weight that needs to be lifted by the machine. In this case, the load is 300N.
2. **Velocity Ratio (VR)** is the ratio of the distance moved by the effort to the distance moved by the load. Given here as 2.
3. **Efficiency** of a machine is expressed as a percentage and is the ratio of the useful work output to the input work done by the effort. Here, the efficiency is 60% or 0.60 as a decimal.
The formula to calculate the **Effort** is derived from the relationship between these factors:
\[ \text{Efficiency} = \frac{\text{Mechanical Advantage (MA)}}{\text{Velocity Ratio (VR)}} \]
Where:
\[ \text{Mechanical Advantage (MA)} = \frac{\text{Load}}{\text{Effort}} \]
From the above, we have:
\[ \text{MA} = \text{VR} \times \text{Efficiency} \]
Replacing with the given values:
\[ MA = 2 \times 0.60 = 1.2 \]
Now, calculate the **Effort** using the relation:
\[ \text{Effort} = \frac{\text{Load}}{\text{MA}} \]
\[ \text{Effort} = \frac{300N}{1.2} = 250N \]
Therefore, the **Effort** needed to lift the load is 250N.