Answer:
The speed of the police car is 294 m/s
Explanation:
Given;
frequency of the siren in air, f = 280 Hz
speed of sound in air, v = 343 m/s
Determine the wavelength of the sound in air to the stationary car:
v = fλ
where;
λ is wavelength of the sound
λ = v/f
λ = 343 / 280
λ = 1.225 m
Now, determine the speed at which the police car is approaching the stationary car;
The actual frequency of the police car, F = 240 Hz
V = Fλ
Where;
V is speed of the police car
λ is the distance between the police car and the stationary car, (wavelength)
V = 240 x 1.225
V = 294 m/s
Therefore, the speed of the police car is 294 m/s
'Frequency' is a word that often confuses some people ... for no good reason.
It just means "frequent-ness" or "often-ness" ... how often something happens.
The SI unit of frequency is the Hertz (Hz). Hz means 'per second'.
So " 13 Hz " means 13 per second.
Here are examples of frequency:
-- 780 kilohertz (on your AM radio dial)
-- 98.7 Megahertz (on your FM dial)
-- 5.8 Gigahertz
-- twice a day
-- three per week
-- every 6 months
Fossil fuels are the largest source of energy in the US.
A 59 kg sprinter, starting from rest, runs 47 m in 7.0 s at constant acceleration.?
What is the sprinter's power output at 2.0 s, 4.0 s, and 6.0 s?
Instantaneous Power is the force times velocity
P = Fv
Because the acceleration is constant, the force will be constant as well
F = ma
P = mav
for constant acceleration, the velocity at each time is found using
v = at
P = ma(at) = ma²t
find the acceleration using kinematic equation
s = ½at²
a = 2s/t²
a = 2(47) / 7.0²
a = 1.918 m/s²
P(2.0) = 59(1.918²)2.0 = 434.25 W = 0.43 kW
P(4.0) = 59(1.918²)4.0 = 868.51 W = 0.87 kW
P(6.0) = 59(1.918²)6.0 = 1302.76 W = 1.3 kW
I hope this helped.
