Power is the rate of work that is done per time. Work is calculated from the product of force and the displacement. So, by using the definition of power and work, we can relate power with force, displacement and the time. We do as follows:
Power = Work / time
Power = Force x displacement / time
Power = 21 N (9 m) / 3 s
Power = 63 J /s = 63 W
Answer: The frequency heard will be f = 275.675Hz
Explanation: When an object emitting sound is moving, it occurs a phenomenon called Doppler shift or Doppler effect. What happens is that the sound gets higher when the moving object comes closer the observer and becomes lower after it passes, This change is due to the quantity of waves that passes through an area in an unit of time.
The formula to calculate the Doppler effect is as follows
f = (
) · f₀
f is the observed frequency;
c is the speed of sound;
Vs is velocity of the source;
f₀ is the emitted frequency of source;
Substituting and calculating,
f =
· 300
f = 275.675 Hz
Thus, the frequency heard by the police officer is 275.675Hz.
Answer:
True
Explanation:
Sound is all about vibrations.
The source of a sound vibrates, bumping into nearby air molecules which in turn bump into their neighbor's, and so forth.
Answer:
Because the gravitational attraction of the Sun hold them in motion around it
Explanation:
For an object travelling in a straight path at constant velocity, the net force acting on the object must be zero.
The planets in the Solar System, however, do not experience a zero net force: in fact, the Sun exerts a gravitational attraction on them, whose magnitude is given by

where
G is the gravitational constant
M is the mass of the Sun
m is the mass of the planet
r is the average distance between the Sun and the planet
Due to the presence of this force, the Sun makes the planets 'deviating' from their straight path, forcing them to following an elliptical path around the Sun.
Answer:
Explanation:
wavelength of sound = velocity / frequency
= 340 / 780
= .4359 m
Let the observer be at equal distance d from in phase source .
let it moves by distance x for destructive interference .
path difference from source
= d + x - (d - x )
= 2x
for destructive interference
path difference = wave length / 2
2x = .4359 / 2 m
x = .4359 / 4
= .108975 m
10.9 cm
so observer must move by distance 10.9 cm towards on of the centers.