The general formula to calculate the work is:
where F is the force, d is the displacement of the couch, and 
is the angle between the direction of the force and the displacement. Let's apply this formula to the different parts of the problem.
(a) Work done by you: in this case, the force applied is parallel to the displacement of the couch, so 
and 
, therefore the work is just equal to the product between the horizontal force you apply to push the couch and the distance the couch has been moved:
(b) work done by the frictional force: the frictional force has opposite direction to the displacement, therefore 
and 
. Therefore, we must include a negative sign when we calculate the work done by the frictional force:
(c) The work done by gravity is zero. In fact, gravity (which points downwards) is perpendicular to the displacement of the couch (which is horizontal), therefore 
and 
: this means
.
(d) Work done by the net force:
The net force is the difference between the horizontal force applied by you and the frictional force:
And the net force is in the same direction of the displacement, so and and the work done is
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
#SPJ1
now you justhave to solve the last numbers because...Iam sooo Lazy right now
85)
The bone structure from outside would be periosteum, cortical, cancellous then medulla. Periosteum is the area outside the bone that will supply nutrition into the outer part of the bone. Cortical is the layer where bone mineral deposition is intense. In this part, the bone is compact and hard. This is the part of the bone that has great strength.
Cancellous is part of the bone where it is not too hard but not too soft. Mineralization is not so dense like cortical layer. That makes this part looks spongy.
In the medulla, most part is made from connective tissue and blood vessels. This part is responsible for the bone vascularization, which means the supply of mineral to the outer part is coming from the medulla. Mineralization is not much in the medulla, makes it not strong. Medulla or marrow also makes blood cells.
86)
The region of the spine would be cervical(neck), thoracal(chest), lumbar(back), sacrum then coccyx. The vertebrae in the neck are smaller since it did not need much strength but need more mobility. Lower part on the thoracal and lumbar is bigger and have a bigger process that will further stabilize the vertebrae. Thoracal vertebrae have a part on their side where the ribs attached. Sacrum shape was a kinda weird because it needs to be able to connect with the pelvis to make buttock. Coccyx the tailbone look like just a small remnant and doesn't seem to have a function in human.
87)
Axis is the name of cervical 2nd vertebral which was located below the atlas, 1st cervical vertebrae. Both of them doesn't have spinal processes that were stabilizing the side of vertebrae Axis also has an odontoid peg which will make the joint with atlas more flexible.
This effect makes the neck can turn to side easily. It also makes neck more mobile vertically, make a nodding movement is possible.
88)
Thre kind of joints would be: Synarthrosis, amphiarthrosis, and diarthrosis.
In synarthrosis, the joint mostly made by fibrous so that it can move. The example of this joint would be suture in the skull. In children, the skull joint is not closed to permit the head to grow but in the adult, it is closed.
Amphiarthrosis joint permits a small movement. This included the intervertebral disc.
Diarthrosis permit a wide degree of movement. This joint is more complex because it has the synovial membrane. The complex structure makes the joints more durable to shock. This was vital because organ with this join used frequently. The example of this joints would be femur and pelvic(hip) joints. Joints in arm and leg mostly diarthrosis joint.
A. I just took a quiz on it and A was my answer
