Answer:
D
Explanation:
The negative feedback is responsible for maintaining equilibrium (stability) in a system as it lessens effects, which is contrary to positive feedback which increases reaction and moves a system further away from equilibrium (stability), It does so by amplifying the effects of a product or event and occurs when something needs to happen quickly. e.g
- Insulin lowers down blood sugar levels, so when the body detects that it has too much sugar, the pancreas is prompted to release insulin and only stops when balance is achieved; hence, negative feedback.
- When there is a tear on the skin, a chemical is released. This chemical causes platelets in the blood to activate, hence they release a chemical which signals more platelets to activate, until the wound is clotted, positive feedback.
Answer:
C
Explanation:
- Let acceleration due to gravity @ massive planet be a = 30 m/s^2
- Let acceleration due to gravity @ earth be g = 30 m/s^2
Solution:
- The average time taken for the ball to cover a distance h from chin to ground with acceleration a on massive planet is:
t = v / a
t = v / 30
- The average time taken for the ball to cover a distance h from chin to ground with acceleration g on earth is:
t = v / g
t = v / 9.81
- Hence, we can see the average time taken by the ball on massive planet is less than that on earth to reach back to its initial position. Hence, option C
<span>
The purpose of a gasoline car engine is to convert gasoline into motion
so that your car can move. Currently the easiest way to create motion
from gasoline is to burn the gasoline inside an engine.
Therefore, a car engine is an internal combustion engine -- combustion takes place internally.
There is such a thing as an external combustion engine. A steam engine
in old-fashioned trains and steam boats is the best example of an
external combustion engine. The fuel (coal, wood, oil, whatever) in a
steam engine burns outside the engine to create steam, and the steam
creates motion inside the engine. Internal combustion is a lot more
efficient (takes less fuel per mile) than external combustion, plus an
internal combustion engine is a lot smaller than an equivalent external
combustion engine. This explains why we don't see any cars using steam
engines.
To understand the basic idea behind how a reciprocating internal
combustion engine works, it is helpful to have a good mental image of
how "internal combustion" works.
One good example is an old Revolutionary War cannon. You have probably
seen these in movies, where the soldiers load the cannon with gun powder
and a cannon ball and light it. That is internal combustion, but it is
hard to imagine that having anything to do with engines.
A potato cannon uses the basic principle behind any reciprocating
internal combustion engine: If you put a tiny amount of high-energy fuel
(like gasoline) in a small, enclosed space and ignite it, an incredible
amount of energy is released in the form of expanding gas. You can use
that energy to propel a potato 500 feet. In this case, the energy is
translated into potato motion. You can also use it for more interesting
purposes. For example, if you can create a cycle that allows you to set
off explosions like this hundreds of times per minute, and if you can
harness that energy in a useful way, what you have is the core of a car
engine! </span>
Answer: oceanic crust moved over the hot spot, each recently formed volcano was carried away from the hot spot toward the northwest, cutting off its source of lava. Meanwhile, a new island was forming so that over time a chain of islands was produced extending away from the hot spot.ANSWER HERE: This mean that volcanos are producing these new islands and it is creating a chain of different islands all over Hawaii.
Answer:
t is time in s For example, a car accelerates in 5 s from 25 m/s to 3 5m/s. Its velocity changes by 35 - 25 = 10 m/s. Therefore its acceleration is 10 ÷ 5 = 2 m/s2
Explanation:
