The frequency of the wave is 50 Hz
Explanation:
The frequency of the wave is defined as the number of cycles per second of the wave:

where
N is the number of cycles completed in a time t.
Frequency is measured in Hertz (Hz).
In this problems, the wave has
N = 100 pulses
in
t = 2.0 s
Therefore, its frequency is

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Answer:
a. speed, v = 0.97 c
b. time, t' = 20.56 years
Given:
t' = 5 years
distance of the planet from the earth, d = 10 light years = 10 c
Solution:
(a) Distance travelled in a round trip, d' = 2d = 20 c = L'
Now, using Length contraction formula of relativity theory:
(1)
time taken = 5 years
We know that :
time = 
5 =
(2)
Dividing eqn (1) by v on both the sides and substituting eqn (2) in eqn (1):
Squaring both the sides and Solving above eqution, we get:
v = 0.97 c
(b) Time observed from Earth:
Using time dilation:


Solving the above eqn:
t'' = 20.56 years
Well the obvious you will crash literally
When a woman walks south at a speed of 2.0mph for 60 minutes. She then turns around and walks north at a distance of 3000m in 25 minutes. then the woman's average speed during her entire motion would be 73.15 meters /minute.
<h3>What is speed?</h3>
The total distance covered by any object per unit of time is known as speed.
the mathematical expression for speed is given by
speed = total; distance /total time
As given in the problem a woman walks south at a speed of 2.0mph for 60 minutes
60 min = 1 hour
1 mile = 1.60934 km
The distance covered by her southwards = speed ×time
=2 mph × 60 minutes
= 3.218 km
She then turns around and walks north at a distance of 3000m in 25 minutes
The distance covered northward is 3000m
speed = total distance /total time
=(3218 +3000) /(60+25)
=73.15 meters /minutes
Thus, The average speed of the woman would be 73.15 meters /minute.
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