Answer: You use it to cook food so you can eat. put whatever kind of food you like in there and heat it up for how long you want and then it will beep when done. then you can eat!
I think so it ans wold be d.because if the source approaches the observer more and more wavefront will pass and it get squeezed.so wavelength decreases and frequency increases.
Answer:
The work done by gravity during the roll is 490.6 J
Explanation:
The work (W) is:

<em>Where</em>:
F: is the force
d: is the displacement = 20 m
The force is equal to the weight (W) in the x component:

<em>Where:</em>
m: is the mass of the bowling ball = 5 kg
g: is the gravity = 9.81 m/s²
θ: is the degree angle to the horizontal = 30°
Now, we can find the work:
Therefore, the work done by gravity during the roll is 490.6 J.
I hope it helps you!
The gravitational force is inversely proportional to the
square of the distance between their centers. So the
force is greatest when the distance is zero.