The correct answer is:
Work is negative, the environment did work on the object, and the energy of the system decreases.
In fact, the work-energy theorem states that the work done by the system is equal to its variation of kinetic energy:
In this problem, the variation of kinetic energy 
is negative (because the final velocity is less than the initial velocity), so the work is negative, and this means that the environment did work on the object, and its energy decreased.
<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: Acceleration due to gravity
Explanation: Force, F = mg, is a vector quantity because the acceleration due to gravity, g, is a vector quantity. Explanation: F = mg Where m is the mass (in kilograms) of the object in question and g is the acceleration due to gravity. Mass is a scalar quantity; mass has no dependence on direction whatsoever.
Answer:
The nearest plant (A) receives 4 times more radiation from the farthest plant
Explanation:
The energy emitted by the star is distributed on the surface of a sphere, whereby intensity received is the power emitted between the area of the sphere
I = P / A
P = I A
The area of the sphere is
A = 4π r²
Since the amount of radiation emitted by the star is constant, we can write this expression for the position of the two planets
P = I₁ A₁ = I₂ A₂
I₁ / I₂ = A₂ / A₁
Suppose index 1 corresponds to the nearest planet,
r2 = 2 r₁
I₁ / I₂ = r₁² / r₂²
I₁ / I₂ = r₁² / (2r₁)²
I₁ / I₂ = ¼
4 I₁ = I₂
The nearest plant (A) receives 4 times more radiation from the farthest plant
Answer:
a) t = 0.528 s
b) D = 1.62 m
Explanation:
given,
speed of the baseball = 3.75 m/s
angle made with the horizontal = 35°
height of the roof edge = 2.5 m
using equation of motion
4.9 t² + 2.15 t - 2.5 = 0
on solving the above equation
t = 0.528 s
b) D = v cos θ × t
D = 3.75 × cos 35° ×0.528
D = 1.62 m
