Answer:
It cancels recoil.
Explanation:
For each action there is an equal an opposite reaction.
The principle of conservation of momentum tell us that if a single spore were ejected the fern would suffer a recoil from it. This recoil would take energy and speed from the spore. But if they are ejected in pairs the recoil is canceled and all the energy is transferred to the spores resulting in higher speeds.
Answer:
When the metal wire in an incandescent lightbulb glows when the light is switched on and stops glowing when it is switched off, this is an example of resistance, which provides light and heat.
Explanation:
Answer:
contains many young stars
Explanation:
Irregular galaxies have <em>no definite shape</em>, which means that the first option is incorrect. They are definitely not round.
However,<u> they contain many young stars because the degree of star formation is fast.</u> They also contain old stars. Thus, the second choice is correct.
The "spiral galaxy" is the type of galaxy that has arms that extend from the center. These arms look "spiral," which influenced its name. This makes the last choice incorrect.
They are actually <u>smaller than the other types of galaxies.</u> This makes them <em>prone to collisions</em>. This makes the last choice incorrect.
Answer: Because new theories can come out that better explain observations and experimental results can replace old theories.
Explanation: Theories more than ten years old are usually out of date. Scientists want to prove that the work of other scientists is wrong. New evidence that supports a change prompts scientists to modify earlier theories.
