Answer:
a)30.14 rad/s2
b)43.5 rad/s
c)60633 J
d)42 kW
e)84 kW
Explanation:
If we treat the propeller is a slender rod, then its moments of inertia is
a. The angular acceleration is Torque divided by moments of inertia:
b. 5 revolution would be equals to 
rad, or 31.4 rad. Since the engine just got started
c. Work done during the first 5 revolution would be torque times angular displacement:
d. The time it takes to spin the first 5 revolutions is
The average power output is work per unit time
or 42 kW
e.The instantaneous power at the instant of 5 rev would be Torque times angular speed at that time:
or 84 kW
At critical temperature, the resistivity of the superconductor
B. It suddenly drops to zero
Explanation:
Materials can be classified into three different types depending on their resistance:
- Conductors: these materials have generally low resistance and allow electricity to pass through easily. The resistance of a conductor increases linearly with the temperature
- Insulators: these materials do not allow electricity to pass through - so they have very high resistance
- Semi-conductors: these are materials that are insulators are room temperature, however they becomes conductors when heated. Therefore, the resistance of a semiconductor decreases when the temperature increases
- Superconductors: these are special materials that are normally conductors; however, at very low temperatures (we are talking about temperature very near to 0 K), their resistance becomes suddenly zero.
Therefore, the correct answer is:
B. It suddenly drops to zero
Learn more about current and resistance:
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#LearnwithBrainly
Barometer duhhhh what’s else a ruler
some form of destructive interference. if phase is 180 degrees out, destructive = darkfringe or quiet in sound
Answer:
a)11.6m
b)45.55s
Explanation:
A body that moves with constant acceleration means that it moves in "a uniformly accelerated movement", which means that if the velocity is plotted with respect to time we will find a line and its slope will be the value of the acceleration, it determines how much it changes the speed with respect to time.
When performing a mathematical demonstration, it is found that the equations that define this movement are as follows.
Vf=Vo+a.t (1)\\\\
{Vf^{2}-Vo^2}/{2.a} =X(2)\\\\
X=Xo+ VoT+0.5at^{2} (3)\\
X=(Vf+Vo)T/2 (4)
Where
Vf = final speed
Vo = Initial speed
T = time
A = acceleration
X = displacement
In conclusion to solve any problem related to a body that moves with constant acceleration we use the 3 above equations and use algebra to solve
a)
for this problem
Vo=0
Vf=319m/min=5.3m/s
a=1.2m/s^2
we can use the ecuation number 1 to calculate the time
t=(Vf-Vo)/a
t=(5.3-0)/1.2=4.4s
then we use the ecuation number 3 to calculate the distance
X=0.5at^2
X=0.5x1.2x4.4^2=11.6m
b)second part
We know that when the elevator starts to accelerate and decelerate, it takes a distance of 11.6m and a time of 4.4s, which means that if the distance is subtracted 2 times this distance (once for acceleration and once for deceleration)
we will have the distance traveled in with constant speed.
With this information we will find the time, and then we will add it with the time it takes for the elevator to accelerate and decelerate
X=218-11.6x2=194.8m
X=VT
T=X/v
t=194.8/5.3=36.75s
Total time=36.75+2x4.4=45.55s
