Energy is required to change the phase of a substance, such as the energy to break the bonds between molecules in a block of ice so it may melt.
During a phase change energy my be added or subtracted from a system, but the temperature will not change. The temperature will change only when the phase change has completed.
The heat Q required to change the phase of a sample of mass m is given by
Q
=
mL
f
(melting or freezing) and
Q
=
mL
v
(evaporating or condensing), where Lf and Lv are the latent heat of fusion and the latent heat of vaporization, respectively.
Key Terms
latent heat of fusion: the energy required to transition one unit of a substance from solid to liquid; equivalently, the energy liberated when one unit of a substance transitions from liquid to solid.
latent heat of vaporization: the energy required to transition one unit of a substance from liquid to vapor; equivalently, the energy liberated when one unit of a substance transitions from vapor to liquid.
sublimation: the transition of a substance from the solid phase directly to the vapor state such that it does not pass through the intermediate, liquid phase
Answer:
d. conduction
Explanation:
Conduction involves the transfer of electric charge or thermal energy due to the movement of particles. When the conduction relates to electric charge, it is known as electrical conduction while when it relates to thermal energy, it is known as heat conduction.
In the process of heat conduction, thermal energy is usually transferred from fast moving particles to slow moving particles during the collision of these particles. Also, thermal energy is typically transferred between objects that has different degrees of temperature and materials (particles) that are directly in contact with each other but differ in their ability to accept or give up electrons.
Any material or object that allow the conduction (transfer) of electric charge or thermal energy is generally referred to as a conductor. Conductors include metal, steel, aluminum, copper, frying pan, pot, spoon etc.
In conclusion, conduction typically involves the transfer of heat energy by direct contact between two or more conductors such as a pot and electric cooker.
for the truck :
M = mass of the truck = 20000 kg
V = speed of truck = 110 km/h = 110 (km/h) (1000 m/1 km) (1 h/3600 sec) = 30.6 m/s
kinetic energy of truck is given as
KE₁ = (0.5) M V²
inserting the values
KE₁ = (0.5) (20000) (30.6)² = 9363600 J
for the astronaut :
m = mass of astronaut = 80 kg
v = speed of astronaut = 27500 km/h = 27500 (km/h) (1000 m/1 km) (1 h/3600 sec) = 7638.9 m/s
kinetic energy of astronaut is given as
KE₂ = (0.5) m v²
inserting the values
KE₂ = (0.5) (80) (7638.9)²
KE₂ = 2.33 x 10⁹ J
Ratio of kinetic energy of truck with kinetic energy of astronaut is given as
KE₁ /KE₂ = (9363600)/(2.33 x 10⁹)
KE₁ /KE₂ = 0.00402
kinetic energy of truck is 0.00402 time the kinetic energy of astronaut.
Acceleration = (change in speed) / (time for the change)
Change in speed = (New speed) - (old speed)
Change in speed = (0.8 m/s - 0.5 m/s) = 0.3 m/s
Time for the change = 3 seconds
Acceleration = (0.3 m/s) / (3 s)
<em>Acceleration = 0.1 m/s²</em>
(a hair more than 1 percent of 1 G.)
The answer to the first question is D. Sun.
For the next one the answer is D. The water droplets fall to earth as rain.
Next one is the Sun I think. Hope these answers help (sorry if I missed one, the numbers were a little wonky)