Answer:
51.2 mi/h
Explanation:
Total distance, d = 100 miles
First 60 miles with speed 55 mi/h
Next 40 miles with speed 75 mi/h
Time taken for first 60 miles, t1 = 60 / 55 = 1.09 h
Time taken for 40 miles, t2 = 40 / 75 = 0.533 h
Time spent to get stuck, t3 = 20 min = 0.33 h
Total time, t = t1 + t2 + t3 = 1.09 + 0.533 + 0.33 = 1.953 h
The average speed is defined as the ratio of total distance traveled to the total time taken.
Average speed =
Thus, the average speed of the journey is 51.2 mi/h.
Answer:
True, True, False, False, False, False.
Explanation:
The refraction index of a material is given by the formula n=c/v, where c is the speed of light in vacuum and v the speed of light in the material. If a ray of light crosses a boundary between two transparent materials and the medium the ray enters has a larger index of refraction it means that in this new medium the speed of light is smaller than on the other one, and then its wavelength is also reduced since f must remain the same (and ), otherwise there is a discontinuity on number of vibrations per second, which cannot happen. So we know that:
1) The wavelength of the light decreases as it enters into the medium with the greater index of refraction. True.
2) The frequency of the light remains constant as it transitions between materials. True.
3) The speed of the light remains constant as it transitions between materials. False.
4) The speed of the light increases as it enters the medium with the greater index of refraction. False.
5) The frequency of the light decreases as it enters into the medium with the greater index of refraction. False.
6) The wavelength of the light remains constant as it transitions between materials. False.
