The speed of the object increases
Explanation:
We can answer this question by applying the work-energy theorem, which states that the work done on an object is equal to the change in kinetic energy of the object. Mathematically:
where
W is the work done on the object
are the final and initial kinetic energy of the object, respectively
m is the mass of the object
v is its final speed
u is its initial speed
In this case, the force does a positive amount of work on the object, so
This also implies that
And so
And therefore
which means that the speed of the object increases.
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B) Light slows down when it passes into a denser medium.
Answer:
It is explained in the explanation section
Explanation:
When the lift starts going downwards, it will start accelerating downwards. After a while, it will start moving with a constant velocity.
Constant velocity means that acceleration is zero and so the man will not feel any weight loss.
Now, Once the lift achieves constant velocity the acceleration is zero hence he will not experience any weight loss.
However, when the lift is in uniform motion, the lift and the man will fall down with an acceleration(a) that is less than that due to gravity(g) . Thus, the man will feel an apparent weight F which is not equal to zero.
