A police car with its 300-Hz siren is moving toward a warehouse at 30 m/s, intending to crash through the door. The sound bounce
1 answer:
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.
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Answer:
We would not be able to make our way around the earth's surface, to read, to sculpt or to create technology because we cannot see!
Explanation:
The minimum angular separation that can be distinguished by an eye gives the angular resolution of the eye.
Given that the Angular resolution with infrared radiation is = equal to
This resolution is very much greater than that of the eye
The angular resolution that our eyes can see is about at arms length
Angular resolution of infrared = at arms length
We therefore cannot read, sculpt or create technology because we cannot see.
The force per unit of length between two wires carrying current is
where I1 and I2 are the currents in the two wires, while r is the distance between them.
We can see from the formula that the force is proportional to the product between I1 and I2:
so, if we double both I1 and I2, we get a factor 4:
so, the force between the wires will be 4 times the original value.
where I1 and I2 are the currents in the two wires, while r is the distance between them.
We can see from the formula that the force is proportional to the product between I1 and I2:
so, if we double both I1 and I2, we get a factor 4:
so, the force between the wires will be 4 times the original value.
Answer:
b) N = 560 N, c) fr = 138.56 N, d) μ = 0.247
Explanation:
a) In the attachment we can see the free body diagram of the system
b) Let's write Newton's second law on the y-axis
N + T_y -W = 0
N = W -T_y
let's use trigonometry for tension
sin θ = T_y / T
cos θ = Tₓ / T
T_y = T sin θ
Tₓ = T cos θ
we substitute
N = W - T sin 30
we calculate
N = 640 - 160 sin 30
N = 560 N
c) as the system goes at constant speed the acceleration is zero
X axis
Tₓ - fr = 0
Tₓ = fr
we substitute and calculate
fr = 160 cos 30
fr = 138.56 N
d) the friction force has the formula
fr = μ N
μ = fr / N
we calculate
μ = 138.56 / 560
μ = 0.247
