Answer:
so sorry
don't know but please mark me as brainliest please
<u>The answer is not contained detail explanation, just a solution and the required values. </u>
All the details are in the pictures, the answers are marked with orange colour.
Note,
in the task no 20.:

V - the velocity of the pair of the balls after collision.
in the task no 21:
m₁ - the mass of the copper ball; m₂ - the mass of the copper calorimeter; m₃ - the mass of the water; t₀ - the initial temperature of water in the copper calorimeter; θ - the final temperature in the calorimeter after the copper ball is transferred into a copper calorimeter; t₁ - the required initial temperature of the copper ball before it is transferred into the calorimeter.
Answer:
6. A
7. C
8. B
9. The average speed is the distance (a scalar quantity) per time ratio. Speed is ignorant of direction. The average velocity is the displacement or position change (a vector quantity) per time ratio.
Answer:
OPTION D (The waves will sometimes get very high and very low) is the answer.
Explanation:
Wavelength = velocity ÷ frequency
As the frequency which measures the number of waves per unit of time is inversely proportional to the wavelength, point X which lies between two sources, and one source is shorter than another, the wave heights at point x will vary as the distances from point X vary too. This means that waves at point X depending on the wave type and source will get very high at times and very low.
Acceleration can be any change in speed, increasing or decreasing.
You haven't said whether the ball is speeding up or slowing down.
If its acceleration is positive ... speed is increasing ... then in 2.5 seconds,
it GAINS (0.5 m/s² x 2.5 sec) = 2.5 m/s of speed. Added to its initial
speed of 2.0 m/s, it ends up moving at 4.5 m/s.
If its acceleration is negative ... speed is decreasing ... then in 2.5 seconds,
it LOSES (0.5 m/s² x 2.5 sec) = 2.5 m/s of speed. Added to its initial
speed of 2.0 m/s, it ends up moving at -0.5 m/s. That means that it ends up
moving in the opposite direction compared to its direction at the beginning of
the change.