a. By the work-energy theorem, the total work required to stop the car is equal to the change in its kinetic energy,
<em>W</em> = 0 - 1/2 (750 kg) (25 m/s)² ≈ -230 kJ
b. The car covers a distance <em>x</em> as it stops such that
<em>W</em> = (-725 N) <em>x</em> ==> <em>x</em> ≈ 320 m
The Doppler Effect...
<span>It describes an increase (or decrease) in the frequency of sound, light, or other waves as the source and observer move toward (or away from) each other.</span>
Kinetic energy = (1/2) (mass) (speed squared)
Kinetic energy = (1/2) (400 kg) (17 m/s)²
Kinetic energy = (1/2) (400 kg) (289 m²/s²)
<em>Kinetic energy = 57,800 Joules</em>
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(That's some amazing house. I'd like to be there to see it.)
I think it's an hour and a half
Explanation:
The speed of a wave is given by :
......(1)
(i) Here, the wavelength of a sound wave in air reduces by a factor of 3. Equation (1) becomes :

Wavelength and frequency are inversely proportional to each other. So, if wavelength of a sound wave in air reduces by a factor of 3, then the frequency will increases by a factor of 3.
(ii) It remains the same.