Answer:
Explanation:
The index of refraction is equal to the speed of light c in vacuum divided by its speed v in a substance, or 
. For our case we want to use 
, which for our values is equal to:
Which we will express with 3 significant figures (since a product or quotient must contain the same number of significant figures as the measurement with the <em>least</em> number of significant figures):
Answer:
Explanation:
Net external force that exerted on the block is given as
here we know that
now we have
so we have
now the force exerted by bigger block on smaller block is given as
now we know that two blocks will exert equal and opposite force on each other
so here the force exerted by 2 kg block on 4 kg block will be
A thermostat is a switch that operates itself when the temperature
goes above or below a temperature that the user can set.
-- Before you go to bed, you set the thermostat for 65° .
If the temperature in the house goes below 65° during the night,
the thermostat turns on the furnace, and keeps it running until
the house warms up to 65°. Then it shuts the furnace off.
-- After breakfast, you set the thermostat for 75°.
If the temperature in the house goes above 75°, during the day,
the thermostat turns on the air conditioner, and keeps it running until
the house cools down to 75°. Then it shuts the air conditioner off.
-- On Sunday morning, you put the slow cooker on the kitchen counter,
and you throw in a big roast, a sliced onion, some baby carrots, some
sliced potatoes, some vegetable stock, salt, pepper, garlic, chili powder,
and tomato paste. Then you put the cover on, turn the power on, and
set the slow cooker to "LOW". The heater in the slow cooker turns on.
Whenever the temperature in the crock gets higher than 160°, the
thermostat in the slow cooker turns off the heater, and keeps it off
until the crock cools down to 160°. Then the thermostat turns the
heater on again.
By dinner time, you have a hot, juicy, scrumptious pot roast, ready
to eat. It's not too hot, not too cold, not too tough, not dried out, and
it melts in your mouth.
You're still thinking about it when you go to bed, and your mom gives you
a slice to take to school for your lunch on Monday.
physics
:p
Mechanical energy is commonly referred to as "the ability to do work." This is a somewhat inaccurate (though still useful) idea of it, as I'll describe.
Mechanical energy is the sum of kinetic energy (energy associated with motion) and potential energy (energy associated with position). Technically speaking, heat energy (the most common example of non-mechanical energy) is small-scale kinetic energy, but for macroscopic systems, this energy is not mechanical. Although it has the ability to do work, it is small-scale and thus not considered "mechanical."
As far as how mechanical energy is transformed into nonmechanical energy, let me provide a couple of examples:
One is the classic example of friction. When two surfaces rub together, they generate thermal energy, or heat. This is a transformation of the mechanical kinetic energy of the objects into the thermal non-mechanical energy (which is small-scale kinetic energy). This is the primary reason why there are no perfect machines--some energy is always lost as heat due to friction.
Another example is a small electric generator. Rotating a small circuit in a magnetic field will induce a voltage and generate electrical non-mechanical energy. This is a transformation of the kinetic energy associated with the rotation into electrical energy.
The primary difference between mechanical energy and non-mechanical energy is the scope. Mechanical energy is generally associated with macroscopic objects (like water wheels), while non-mechanical energy is generally on the sub-microscopic scale (the kinetic energy of individual atoms). Both can do work, though working with mechanical energy is generally more helpful than trying to work with non-mechanical energy.
