C.
Explanation: Because mirrors are lighter, and they are easier than lenses to make perfectly smooth.
If you increase the frequency of a sound wave four times, t<span>he speed will increase four times. The correct option among all the options that are given in the question is the first option or option "A". This also shows the frequency and speed of the waves are directly proportional to each other. I hope it helps you.</span>
Answer:
Explanation:
Given
Cross-sectional area of two areas is
It is filled with oil of density 
mass of car place on Large area 
Suppose a mass of m kg is placed on smaller area
According to pascal law's intensity of pressure is same at every point on Liquid
Answer;
Average speed = 47.5 km/hr
Explanation and solution;
Average Speed = Total distance /Total time
Total distance;
-In the first two hours travelling at 40km/hr, total distance traveled is 80km.
(40 × 2) = 80 km
-In next two hours distance covered is 110 km. (55 ×2)
Total distance = 110 + 80 = 190 km
Total time = 2 + 2 = 4 hours
Average Speed = Total distance /Total time
= 190/4
= 47.5 km/hr
