Answer:
Any incident ray traveling parallel to the principal axis of a converging lens will refract through the lens and travel through the focal point on the opposite side of the lens. ... These rays of light will refract when they enter the lens and refract when they leave the lens.
Hope this helps...
THE DOPPLER EFFECT. Anyways, it would have a higher whistle as it approaches you, when it gets to you it only gets quieter because it leaves after. Think of a motorcycle going by, its loud coming to you then as it passes it gets quieter.
Answer:
Question 1)
a) The speed of the drums is increased from 2 ft/s to 4 ft/s in 4 s. From the below kinematic equations the acceleration of the drums can be determined.

This is the linear acceleration of the drums. Since the tape does not slip on the drums, by the rule of rolling without slipping,

where α is the angular acceleration.
In order to continue this question, the radius of the drums should be given.
Let us denote the radius of the drums as R, the angular acceleration of drum B is
α = 0.5/R.
b) The distance travelled by the drums can be found by the following kinematics formula:

One revolution is equal to the circumference of the drum. So, total number of revolutions is

Question 2)
a) In a rocket propulsion question, the acceleration of the rocket can be found by the following formula:

b) 
The vector sum of forces acting on a non-accelerating object equals zero.
equation form: ΣF = 0
1) <span>The function of the electron transport chain is to pump protons in the mitochondrion inter-membrane, thus building up a proton gradient. This gradient will allow the ATP syntheses</span><span>.</span>
2) Why we need oxygen for the electron transport chain:
At the end of the electron transport chain is the Oxygen that will accept
electrons and picks up protons to form water. If the oxygen molecule is not there the electron transport chain
will stop running, and ATP will no longer be produced. Basically, we need the oxygen to produce more ATP.