Answer: D. 
Explanation:
The energy 
of an electromagmetic wave is given by:
Where:
is the Planck constant
is the speed of light in vacuum
Then 
is the wavelength
Solving:
Answer:
Average speed, As = 2.2 [m/s]
Explanation:
To solve these types of problems we must remember that the average of the speeds is determined by dividing the distance over time.
With the first speed and the time of 6 [s] we can calculate the distance.
V = x/t
where:
x = distance [m]
V = velocity = 1.1 [m/s]
t = time = 6 [s]
x1 = V*t
X1 = 1.1*6
X1 = 6.6 [m]
Now with the second velocity and 6 [s], we can calculate the second distance.
X2 = 3.3*6
X2 = 19.8 [m]
Now we have to calculate the average speed. The total distance is x = x1 +x2
X = 19.8 + 6.6 = 26.4 [m]
and the total time is 12 [s]
Therefore:
As = 26.4/12
As = 2.2 [m/s]
Answer:
Correct answer letter b.
Explanation:
When the book is on the top shelf of the bookcase, it just only gravitational potential energy, due to the gravitational field and the kinetic energy at this point is zero because the book is at rest.
Now, when the book starts falling, all the potential energy will transform into the kinetic energy. It happens, thanks to the conservation of the energy,that says energy can neither be created nor destroyed, energy can only be transferred or changed from one form to another.
Let's recall that the gravitational potential energy depends on the object's position, so when the book falls, the magnitude of the position decreases and the speed of this object increases.
Therefore, the potential energy of the book decreases as kinetic energy increases.
Correct answer letter b.
I hope it helps you!
Answer:
cross out the false piece in blue and write the true piece in red
Answer:
a) 1.75s b) 17.2 m/s (down)
Explanation:
d1= 15m d2= 0m (because it hits ground)
a= -9.81 m/s^2 t=???
Equation
the triangle means change in so d2-d1
Δd= v1 * t + 1/2 * a * t^2
0m-15m= v1*t + 1/2 a t^2
-15 m= 0m/s*t (goes away) + 1/2* a *t^2
-15mx2= t^2
-15mx2/a= t^2
Square root (-30/-9.81m/s^2)
t=1.75 s
b) now v2!!
Im going to use v2= v1 + a*t
v2= 0m/s + -9.81 x 1.75s
v2 = -17.2 m/s or you can say 17.2 m/s down!!!
