Answer:
b. There is no definite top to the atmosphere. The pressure and density gradually get smaller as the altitude gets larger.
Explanation:
There is no specific top of the atmosphere. It varies from place to place. But generally it is considered to be 480 kilometers thick. But majority of its thickness is limited to 16 km only above earth surface. The pressure and density gradually get smaller as the altitude gets larger. The air pressure at sea level is 14.7 pounds per square inch and it decreases to 10 pounds per square inch at a height of 3 kilometers. From the above discussion we say that option B is correct
Copper is a better conductor.
Angular velocity is the rate of change of angle of a body, i.e. omega = v / r = (2*pi*r)/ r*t = (2*pi)/ T. where T is the time period of whatever is rotating and r is the radius of the circle. So if a circular disc is spinning at 1 m/s then the angular velocity of it is 2*pi radians/ second.
5 a)
Start by arranging the materials by the sonic speed and then their physical state:
- Copper (solid)
- Glass (solid)
- Wood (solid)
- Sea Water (liquid)
- Acetone (liquid)
- Alcohol (liquid)
- Helium (gas)
- Carbon dioxide (gas)
What trend do you identify from these data? Here's what I've got:

5 b)
The way microscopic particles are arranged in a substance helps distinguish between different physical states:
- Particles in a solid are held tightly in place with small separation in between; it's hard for particles in a solid to move past one another; solids therefore have shapes that persists over time.
- Particles in a gas are highly mobile- they keep moving AT ALL TIMES. There are large separations between individual particles and therefore gases tend to show no definite shape or volume.
- The arrangement of particles in a liquid is located somewhere in between that of solids and gases. The exact configuration is dependent on the nature of the liquid- for example, molecules in maple syrup are held way closer to each other than those in distilled water are.
Sound travels as a longitudinal wave. As a sound wave passes through a medium, individual particles become excited and gain energy; as they run into others they transfer their energy to the next particle; the sound wave thus propagate across the medium. With a lower average distance between individual particles this action can proceed at a greater rate in average solids than in average liquids, and in average liquids than in average gases. Hence the trend.