The mirror formula for curved mirrors is:
![\frac{1}{f}= \frac{1}{d_o}+ \frac{1}{d_i}](https://tex.z-dn.net/?f=%20%5Cfrac%7B1%7D%7Bf%7D%3D%20%5Cfrac%7B1%7D%7Bd_o%7D%2B%20%5Cfrac%7B1%7D%7Bd_i%7D%20%20%20)
where
f is the focal length of the mirror
![d_o](https://tex.z-dn.net/?f=d_o)
is the distance of the object from the mirror
![d_i](https://tex.z-dn.net/?f=d_i)
is the distance of the image from the mirror
The sign convention that should be used in order to find the correct values is the following:
-
![f](https://tex.z-dn.net/?f=f)
: positive if the mirror is concave, negative if the mirror is convex
-
![d_i](https://tex.z-dn.net/?f=d_i)
: positive if the image is real (located on the same side of the object), negative if it is virtual (located on the opposite side of the mirror)
The warm air rises, because it has become less dense as a result of increase in temperature from heating. Since it is heated, it expands and becomes less dense and such it rises.
The cold air, as result of decrease in temperature contracts, and becomes denser. The cold air is denser than the warm air. The cold air, being the denser sinks. So the cold air sinks because it is denser and heavier than warm air.
The sound takes 0.2 seconds to go to the hill and come back, so it would take 0.1 seconds to get to the hill. then v=d/t; v=33.2/0.1
v=332m/s
Answer: height = 3.98m
Explanation: by placing the watermelon at a height above the ground, it has a potential energy of the formulae
p = mgh
p = potential energy = 4.61kJ = 4610J
m = mass of watermelon = 118 kg
g = acceleration due gravity = 9.8 m/s²
4610 = 118 * 9.8 * h
h = 4610/ 118 * 9.8
h = 4610/ 1156.4
h = 3.98m