Let's use ' t ' to represent half of the time, in hours.
The distance traveled in the first half of the time is (80 t) km.
The distance traveled in the last half of the time is (40 t) km.
The total distance covered is (80t + 40t) = (120t) km.
You said that the total distance covered was 60 km,
so ...
120 t = 60 km
Divide each side by 120 : t (half of the time) = 0.5 hour
Average speed = (total distance covered) / (time to cover the distance)
= (60 km) / (1 hour)
= 60 km/hr .
diameter of earth in miles= 7928 miles
1 mile = 1.609 km
diameter of earth in km= 7928*1.609
=12,756.152 km
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Answer:
frequency = 1475.45 Hz
Explanation:
given data
frequency f1 = 1215 Hz,
frequency f2 = 1265 Hz
police car moving vp = 25.0 m/s
solution
speed of sound u = 343 m / s
speed of the other car = v
when the police car is stationary
the frequency the other car receives is
f2 = f1 ×
................1
and
the frequency the police car receives is
f2 = f1 ×
..................2
now from equation 1 and 2


v = 4.77 m/s
and
frequency the other car receives is
f2 = f1 ×
......................3
and
the frequency the police car receives is
f2 = f1 ×
.......................4
now we get
f2 = f1 ×
f2 =
f2 = 1475.45 Hz