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.
"(1) a satellite moving around Earth in a circular <span>orbit" is the only option from the list that describes an object in equilibrium, since velocity and gravity are working together to keep the orbit constant. </span>
Answer:
14.43° or 0.25184 rad
Explanation:
v = Speed of sound in air = 343 m/s
f = Frequency = 1240 Hz
d = Width in doorway = 1.11 m
Wavelength is given by

In the case of Fraunhofer diffraction we have the relation

The minimum angle relative to the center line perpendicular to the doorway will someone outside the room hear no sound is 14.43° or 0.25184 rad