The correct answer is:
<span>C) The actual frequency of the siren does not change despite appearances.
In fact, Bob will observe an increase in the apparent frequency as the emergency vehicle approaches him, while Jill will observe a decrease in the apparent frequency as the emergency vehicle moves away from him, because of the Doppler effect (the relative velocity between the observer and the source of the sound is changing), but this effect involves the apparent frequency, while the real frequency of the siren will remain the same.</span>
Answer:
Explanation:
The equation for this is
where f is the frequency, v is the velocity, and lambda is the wavelength. Filling in:
and
which means that
the wavelength is 1.37 m, rounded to the correct number of significant digits.
Answer:
A kilowatt (kW) is a unit of power.
Explanation:
The power of an object is given by :
Here,
E is the energy required
t is time
The SI unit of power is Watts and the SI unit of energy is Joule. the commercial unit of energy is kilowatt per hour.
Option (1) : A kilojoule (kJ) is a unit of power is incorrect.
Option (2) : A gigawatt (GW) is a unit of energy is incorrect.
Option (3) : A watt (W) is a unit of energy is incorrect.
Option (4) : A kilowatt x hour per year (kWh/yr) is a unit of energy is incorrect.
Option (4) : A kilowatt (kW) is a unit of power is correct.
Hence, the correct option is (d).
Explanation:
Resonance: Resonance is the phenomenon which occurs when the applied frequency on the object is equal to its natural frequency.
In the given problem, the singing of an opera singer caused a drinking glass to shatter.
This occurs due to the phenomenon resonance. The applied frequency of the singing of an opera singer on the drinking glass matches with the natural frequency of the drinking glass. It causes a glass to shatter.
Answer:
<em>When a balloon deflates air moves out of the balloon </em><em>because the pressure inside the balloon is higher than the pressure outside the balloon.</em>
Explanation:
An inflated balloon has a high pressure region on its inside. Gases always move from a region of high pressure to a region of low pressure. When a balloon is inflated its membrane stretches making it even more porous.
The gas molecules inside the balloon easily diffuse out through this membrane. The diffusion rate may differ depending on the type of gas filled inside the balloon and the material of the balloon. For example helium balloon deflates faster than common air balloon.
This is because helium is a light element and can escape easier than gases like nitrogen and oxygen through the porous membrane of the balloon.
