The answers to question 4 d
Answer:
Part 1) Time of travel equals 61 seconds
Part 2) Maximum speed equals 39.66 m/s.
Explanation:
The final speed of the train when it completes half of it's journey is given by third equation of kinematics as
where
'v' is the final speed
'u' is initial speed
'a' is acceleration of the body
's' is the distance covered
Applying the given values we get
Now the time taken to attain the above velocity can be calculated by the first equation of kinematics as
Since the deceleration is same as acceleration hence the time to stop in the same distance shall be equal to the time taken to accelerate the first half of distance
Thus total time of journey equals
Part b)
the maximum speed is reached at the point when the train ends it's acceleration thus the maximum speed reached by the train equals 
Answer: True
Explanation: Following are the properties that are used to identify minerals:
(1) Color
(2) Hardness
(3) Magnetism : It is the property of mineral to attract or repel with other magnetic materials.
(4) Luster : It is the property that shows the surface is reflecting light or not.
(5) Reactivity: Reactivity is also responsible to identify mineral. How the mineral is reacting with acids, bases etc helps to identify type of minerals.
Answer:
#_photon = 7 10²¹ photons
Explanation:
Let's look for the power that affects the panel of area of 1.5 m2
I = P / A
P = I A
P = 1.37 10³ 1.5
P = 2,055 10³ W
P = E / t
If we use t = 1 s
E = P t
E = 2,055 10³ J
This is the power that the panel receives, let's look for the energy of a photon
E = h f
c = λ f
f = c /λ
E = h c /λ
Let's calculate
E₀ = 6.63 10⁻³⁴ 3 10⁸/680 10⁻⁹
E₀ = 2.925 10⁻¹⁹ J
In one second the total energy is the number of photons for the energy of each one
E = #_photon E₀
#_photon = E / E₀
#_photon = 2,055 10³ / 2,925 10⁻¹⁹
#_photon = 7 10²¹ photons
