Answer:
A downward sloped line means the object is returning to the starting point.
Work needed: 720 J
Explanation:
The work needed to stretch a spring is equal to the elastic potential energy stored in the spring when it is stretched, which is given by

where
k is the spring constant
x is the stretching of the spring from the equilibrium position
In this problem, we have
E = 90 J (work done to stretch the spring)
x = 0.2 m (stretching)
Therefore, the spring constant is

Now we can find what is the work done to stretch the spring by an additional 0.4 m, that means to a total displacement of
x = 0.2 + 0.4 = 0.6 m
Substituting,

Therefore, the additional work needed is

Learn more about work:
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<span>The inner planets (in order of distance from the sun, closest to furthest) are Mercury, Venus, Earth and Mars. After an asteroid belt comes the outer planets, Jupiter, Saturn, Uranus and Neptune. The interesting thing is, in some other planetary systems discovered, the gas giants are actually quite close to the sun</span>
Particles that are closely packed but spaced apart enough to move over one another are called plasma. Option C is correct.
<h3>What is the plasma state of matter?</h3>
Plasma is a state of matter wherein particles are tightly packed but are far enough apart to slide over one another.
The following conditions are followed by the plasma state.
Hence, option C is correct.
To learn more about the plasma state refer;
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1 Purpose/Question. Ask a question. 2 Research. Conduct background research. ... 3 Hypothesis. Propose a hypothesis. ... 4 Experiment. Design and perform an experiment to test your hypothesis. ... 5 Data/Analysis. Record observations and analyze the meaning of the data. ... 6 Conclusion. Conclude whether to accept or reject your hypothesis.
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