The fact that no heat is transferred between a system and
its surroundings refers to an adiabatic free expansion.
In gas, the adiabatic compression creates
an increase in the temperature while it causes a drop in temperature there is
adiabatic expansion against pressure, or a spring.
<span>
Before being allowed to expand in vacuum, the gas is first contained in an
insulated container.</span>
The work made by or on the
system is zero since there is no external pressure for the gas to enlarge on against.
The first law of thermodynamics then insinuates
that zero is the net internal energy change of the system since the process
does not incorporate any work or heat transfer.
Lumbar nerves transmit signals that allow us to walk. They are a pivotal part of the human body, and without them we would be immobile. Hope this helps.
Acceleration = (change in speed) / (time for the change).
Change in speed = (15 - 30) = -15 km/hr
Time for the change = 4 sec
Acceleration = (-15 km/hr) / (4 sec) = -3.75 km/hr per second .
Is that a lot ? Not much ?
Let's convert it to a unit that we can think about:
(-15 km/hr) x (1,000 m/km) x (1 hr / 3,600 sec) =
(-15 x 1,000) / (3,600) = -(4 and 1/6) m/sec .
So the acceleration of the bus is -(4 and 1/6) m/sec² .
The negative sign means that it slowed down.
(4 and 1/6) m/sec² is about 42% of the acceleration of gravity ...
the acceleration the bus would have if it drove off of a cliff.
When the car or the bus you're riding in slows down at that rate,
you feel 42% of your weight pulling you forward against your
seat belt. That's quite a drastic acceleration !
