Answer: 4
The mechanical advantage is the ratio of the force exerted by the object to the force applied to do work on it.
Here, Jeff tried to lift a rock weighing 600 pounds by wedging board under the rock. Jeff who weighs 150 pounds uses all his weight to exert force on lever and lift rock.
Mechanical advantage, 
Therefore, the mechanical advantage that lever provided to Jeff in lifting rock is 4.
The basic difference is that the ordinary sources are incoherent that means that the discrete frequencies merge up to give an intermediate between the maximum and minimum frequencies. While the laser is coherent containing the single frequency with maximum amplitude. thus travelling far.
Photovoltaic cells are the most efficient means of converting solar energy to electricity. Option b is correct.
<h3>What is a cell?</h3>
A cell is a voltage and current-producing device that consists of a single anode and cathode separated by an electrolyte.
One or more cells can make up a battery. One cell, for example, is one AA battery.
Light intensity on a solar cell is often measured in "suns," with one sun roughly equivalent to 1 kW/m².
Concentrated sunlight improves the ratio of current generated while the device is lighted vs when it is dark, hence enhancing output voltage and efficiency.
Photovoltaic cells are the most efficient means of converting solar energy to electricity.
Hence, option b is correct.
To learn more about the cell refer to:
brainly.com/question/3142913
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Answer:
A
Explanation:
A. The molecules that make up olive oil are longer than those that
make up alcohol, so they have more resistance to sliding past one
another.
Olive oils are unsaturated fats with many carbons whereas, alcohols are typically short with very few carbons.
Place the object in an electronic balance and measure its mass.
Place a measured amount of water in the cylinder.
Place the object in the cylinder so that it’s fully submerged.
Measure the new level of the liquid and subtract the original level. This is equal to the volume of the object.
Density = mass / volume.