Answer
As the angle of incidence increases in Figure 2.8, a point is finally reached where the refracted ray does not emerge at the second layer but lie along the interface. This particular angle of incidence at which the angle of refraction is 90° and the refracted ray lies along the interface is known as the critical angle. At and beyond the critical angle, there is no transmitted ray and therefore a very high reflected ray will be recorded .
Therefore,
sinθisin90=Vp1Vp2
But, sin 90 = 1.
At critical angle,
sinθcritical=Vp1Vp2
A critical refracted wave travels along the interface between layers and is refracted back into the upper layer at the critical angle. The waves refracted back into the upper layer are called head waves or first-break refractions because at certain distances from a source, they are the first arriving energy. Recorded first-break refraction is shown in Figure 2.10.
Note that these first-break refractions can give us important information about the shallow velocities on land seismic data.
Note also that seismic data are acquired in such a way that reflections from horizons of interest are in the pre-critical region, even at the farthest offset in the data.
In reality, part of the seismic energy arriving at an interface is transmitted and refracted, and another part of the energy is reflected at that same interface. Given that there are many reflectors in the subsurface, there will be many paths from source to receiver, each of them with a different travel time. The proportion of energy reflected depends on the material properties of the two bounding layers and on the angle of incidence
you need G, grav constant, here.
F=GMmoonMEllen/R^2
all other numbers given ... calculate ...
Answer:
B) Angular velocity
Explanation:
The equivalent of Newton's second law for the rotational motions can be written as:
where
is the net torque applied to the object
I is the moment of inertia
is the angular acceleration
From the formula we see that when a constant net torque is applied, then the object also has a constant angular acceleration, .
But we also know that
where 
is the angular velocity: so, a constant angular acceleration means that the angular velocity of the object is changing, so the correct answer is
B) Angular velocity
(moment of inertia and center of gravity do not change since they only depend on the mass and the geometry/shape of the object, which do not change)
1. They have evolved their leaves into spikes for minimum water loss through transpiration.
2. They have a waxy layer for minimum water loss.
3. They have thick walls for minimum water loss.
4. They can take water from atmosphere.
5. They change the photo energy from Sun into an intermediate stage and store it, so that they can make food even in night.
64 miles/hour
Therefore 1/64 hours/mile
68 miles * 1/64 hours/mile (notice how miles cancels out)
Therefore the answer is 68/64 hours = 1.0625 hours = 1 hour 3min and 45sec.
