Answer:
The error he made was that he didn't convert the unit of temperature to Kelvin.
The correct efficiency is 24%
Explanation:
Parameters given:
Temperature of hot reservoir = 100°C = 373 K
Temperature of cold reservoir = 10°C = 273 K
The efficiency of a heat engine is given as:
E = 1 - (Qc/Qh) = 1 - (Tc/Th)
Where
Qc = Output heat;
Qh = Input heat;
Tc = Temperature of the cold reservoir;
Th = Temperature of the hot reservoir.
=> E = 1 - (283/373)
E = 1 - 0.76
E = 0.24
In percentage,
E = 0.24 * 100 = 24%
Hence, the efficiency of the engine is actually 24%.
The error he made was that he didn't convert the temperature to Kelvin. If we leave the temperatures in °C, we have that:
E = 1 - (10/100)
E = 1 - 0.1 = 0.9
In percentage,
E = 0.9 * 100 = 90%
Answer:1.84
Explanation:
Given
Humming bird travels 1.2 m along a straight line at height of 3.4 m
Now bird drops 1.4 m to hover in front of the flower
So bird net displacement is
displacement
displacement
=1.84
Answer:
Explanation:
There are 2 ways to help with this. Explain the details, which are fairly simple in this topic, or give the formula. My hope is that an explanation will last longer than memorizing the formula. I give you both.
If a wave has frequency, f, of 3 Hz, its period, T, is
1
3
s
. The wavelength,
λ
, is 5 meters. That means that in the time of one period, the wave travels 5 m.
In general,
S
p
e
e
d
=
distance
time
In applying this general definition of speed
↑
to a wave, we have
speed of the wave
=
wavelength
period
Note: we generally use v for speed of a wave. Using the variable names, then that last formula is written
v
=
λ
T
Since
T
=
1
f
, we can also say that
v
=
λ
⋅
f
So, using that last formula
v
=
5
m
⋅
3
H
z
=
15
m
s
Note: the unit Hz is equivalent to what it was called 100 years ago,
cycles
second
(
also cps
)
. Cycles is not a true unit, so the Hz contributed only the "per second" to the result
15
m
s
.
Explanation:
If the satellite is moving too quickly then the gravitational attraction between the Earth and the satellite is too weak to keep it in orbit. If this is the case, the satellite will move off into space. This occurs at speeds around or above 11,200 metres per second (m/s).
Answer:
b. light from earth is reflected by the moon surface
