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.
Answer:
steel
Explanation:
steel because steel has more power to hold something up, where bricks arent as stable
Answer:
photoelectric effect
Explanation:
When the energy from photons is absorbed by matter, the matter can emit electrons. This process is called the photoelectric effect. The photoelectric effect is a property of light that is not explained by the theory that light is a wave.
m= 60g = 60/1000 Kg = 0.06 Kg
v = 2cm3 = 2 * (0.01^3) m3 = 2 *10^-6 m3
Density= m/v = 6 * 10^-2 / 2 *10^-6 = 3 *10^4 Kg/m3
Resultant is 5 m/s using the Pythagorean theorem<span />
