Answer:
For a velocity versus time graph how do you know what the velocity is at a certain time?
Ans: By drawing a line parallel to the y axis (Velocity axis) and perpendicular to the co-ordinate of the Time on the x axis (Time Axis). The point on the slope of the graph where this line intersects, will be the desired velocity at the certain time.
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How do you know the acceleration at a certain time?

Hence,
By dividing the difference of the Final and Initial Velocity by the Time Taken, we could find the acceleration.
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How do you know the Displacement at a certain time?
Ans: As Displacement equals to the area enclosed by the slope of the Velocity-Time Graph, By finding the area under the slope till the perpendicular at the desired time, we find the Displacement.
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Answer : The frequency decreases by a factor of 2.
Explanation :
Given that the wave travels at a constant speed. The speed of the wave is given as :

Where
υ is the frequency of the wave
and λ is the wavelength of the wave.
In this case, the speed is constant. So, the relation between the frequency and the wavelength is inverse.

If the wavelength increases by a factor of 2, its frequency will decrease by a factor of 2.
Hence, the correct option is (A) " The frequency decreases by a factor of 2 ".
The latent heat of fusion refers to the solid to liquid or liquid to solid states.
Answer: Option C
<u>Explanation:
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It is known that the inter conversion process from the states of solid to liquid is referred as fusion. So, for these conversions, the external energy in the heat form should be supplied to solid.
This external energy should be greater than the latent heat of solid in order to successfully break the bonds to form liquid. So the change in the enthalpy of the reaction while conversion from solids to liquids are termed as latent heats of fusion.
Even the inter-conversion from liquid to solid state will undergo change in enthalpy where the heat will be released and that is termed as latent heats of solidification. It is found that latent heat of solidification is equal in magnitude but opposite in direction with the latent heats of fusion.