Answer: 
Explanation:
According to the conservation of linear momentum principle, the initial momentum
(before the collision) must be equal to the final momentum
(after the collision):
(1)
In addition, the initial momentum is:
(2)
Where:
is the mass of the comet
is the mass of the asteroid
is the velocity of the comet, which is positive
is the velocity of the asteroid, since it is at rest
And the final momentum is:
(3)
Where:
is the final velocity
Then :
(4)
Isolating
:
(5)

Finally:
This is the final velocity, which is also in the positive direction.
perpendicular to the wave motion.
Answer:
D
Explanation:
From the information given:
The angular speed for the block 
Disk radius (r) = 0.2 m
The block Initial velocity is:

Change in the block's angular speed is:

However, on the disk, moment of inertIa is:

The time t = 10s
∴
Frictional torques by the wall on the disk is:

Finally, the frictional force is calculated as:


Answer:
I think D am not pretty show
Answer:
Microlensing.
Explanation:
This techniques is called Microlensing.
Microlensing is a method of gravitational lensing where light from a backdrop point of origin is curved to develop distorted, numerous and/or lightened images by the gravity field of a foreground lens.
This method is very effective in discovering planets that are far-far from earth.It is actually an astronomical effect that was predicted by Albert Einstein's general theory of relativity.