Explanation:
First, we need to determine the distance traveled by the car in the first 30 minutes,
.
Notice that the unit measurement for speed, in this case, is km/hr. Thus, a unit conversion of from minutes into hours is required before proceeding with the calculation, as shown below

Now, it is known that the car traveled 40 km for the first 30 minutes. Hence, the remaining distance,
, in which the driver reduces the speed to 40km/hr is
.
Subsequently, we would also like to know the time taken for the car to reach its destination, denoted by
.
.
Finally, with all the required values at hand, the average speed of the car for the entire trip is calculated as the ratio of the change in distance over the change in time.

Therefore, the average speed of the car is 50 km/hr.
Answer:
Wegener first thought of this idea by noticing that the different large landmasses of the Earth almost fit together like a jigsaw puzzle. The continental shelf of the Americas fits closely to Africa and Europe, and other continents showed the same trend. Wegner also analyzed both sides of the Atlantic Ocean for rock type, geological structures and fossils and noticed that there was a significant similarity between matching sides of the continents, especially in fossil plants.
Person standing on A will hear the loudest sound
Explanation:
The intensity of a sound wave (which is proportional to the loudness of the sound) follows an inverse square law, which is:

where
I is the intensity of the wave
r is the distance from the source of the sound
This equation means that the intensity of the sound wave (and therefore, its loudness) is inversely proportional to the square of the distance from the source: therefore,
- As we get closer to the source of sound, the loudness increases
- As we move away from the source of sound, the loudness decreases
Therefore, the person that will hear the loudest sound is the one standing closer to the source, and therefore person A.
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Explanation:
The water cycle basically involves five steps:
- evaporation and transpiration ⇄
- condensation, ⇄
- precipitation, ⇄
- runoff, ⇄
- infiltration ⇄
So when a <u>thunderstorm </u>occurs it <em>helps in completing the precipitation process </em>by enabling the release of water vapor stored up in the atmosphere to fall on the ground as rain.
After this, the water <em>runoffs </em><em>to the surface of the ground, on plants, into rocks, rivers, and lakes.</em>
Next, the <em>Infiltration process</em> enables the water on the ground surface to enter the soil some of which becomes groundwater.
The cycle begins again as the<em> </em><em>evaporation and transpiration</em> <em>process </em>begins, where the groundwater as a result of heat from the sun is taken back into the atmosphere, while water in plants by means of transpiration goes back <em>into the atmosphere</em>.
It then <em>condenses </em>and falls back as precipitation again.
Answer:
The glass rod remains charged due to electrification by the silk