The greenhouse effect is a warming effect caused by certain gases that retain heat from sunlight. Without such gases, the average surface temperature of the Earth would be below freezing, and as explained by the Encyclopedia of Environmental Science, “life, as we know it, would not exist.”
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The global warming debate is centered upon whether added greenhouse gases released by human activity will overheat the Earth and cause harmful effects.</span><span>
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Answer: A. The stone thrown upward spends more time in the air.
Explanation:
The stone thrown above the horizontal has an initial vertical speed, whose direction is opposed to gravity. It means that it decelerate first before accelerating in the direction of gravity. Where the stone thrown below the horizontal has an initial vertical speed in the direction of gravity, so there is no deceleration.
In consequence, the stone thrown upward spends more time in the air. Correct answer is option A.
Answer:As an object speeds up, the total energy increases / decreases / remains the same. As an object slows down, the total energy increases / decreases / remains the same.
Explanation:
If all the energy she put into bending the bow is completely
transmitted to the arrow, then the arrow has the 100 joules
of kinetic energy when it leaves the bow.
Kinetic energy = (1/2) (mass) (speed)²
100 J = (1/2) (0.5 kg) (speed²)
Divide each side by 0.25 kg: 100 J / 0.25 kg = speed²
[ joule ] = [ newton-meter ] = kg-m²/sec²
100 kg-m²/sec² / 0.25 kg = speed²
400 m²/sec² = speed²
Take the square root of each side: speed = √400 m/s
20 m/s
(about 44.7 mph)