As the question is about changing in frequency of a wave for an observer who is moving relative to the wave source, the concept that should come to our minds is "
Doppler's effect."
Now the general formula of the Doppler's effect is:
-- (A)
Note: We do not need to worry about the signs, as everything is moving towards each other. If something/somebody were moving away, we would have the negative sign. However, in this problem it is not the issue.
Where,
g = Speed of sound = 340m/s.
= Velocity of the receiver/observer relative to the medium = ?.
= Velocity of the source with respect to medium = 0 m/s.
= Frequency emitted from source = 400 Hz.
= Observed frequency = 408Hz.
Plug-in the above values in the equation (A), you would get:
Solving above would give you,
= 6.8 m/s
The correct answer = 6.8m/s
Answer:
72.98 km
Explanation:
Her displacement is simply the distance from her final position to her initial position.
Now, I've drawn and attached a triangle diagram to depict this her movement.
Point O is her initial starting point.
Point A is the first point she gets to after travelling north while point B is the final point after travelling north east.
From the triangle, the displacement will be the distance OB which is denoted by x and can be solved from cosine rule.
Thus;
x² = 62² + 26² - 2(62 × 26)cos 120
x² = 4520 + 806
x² = 5326
x = √5326
x = 72.98 km
Answer: His average speed in mph over the last 400 m is 7.7 m/s.
Explanation:
Given: Hicham El Guerrouj of Morocco holds the world record in the 1500 m running race. He ran the final 400 m in a time of 51.9 s.
We know that , speed = 
Here , distance = 400m and time = 51.9 s
Then, speed = 
Hence, his average speed in mph over the last 400 m is 7.7 m/s.
Answer:
the correct answer is E
A graph of the cart's maximum speed squared as a function of x^3
Explanation:
For this exercise let's use Newton's second law
F = m a
force has the form
F = k x²
and acceleration is related to velocity
a = dv / dt
Let's use the chain rule or L'Hospital
a = dv /dx dx/dt
a = dv /dx v
let's substitute
k x² = m v dv / dx
k /m x² dx = v dv
we integrate
k /m x³ /3 = v² / 2
v² = (2k /3m) x³
This is the expression for the variation of the speed as a function of the position, to make a linear graph realism the changes of variable
y = v²
x´ = x³
y = (2k/3m) x´
if we graph y vs x 'we have a linear graph whose slope is
m = 2k / 3m
By reviewing the different answers, the correct answer is E
<span>Answer:
For a disc, the moment of inertia about the perpendicular axis through the center is given by 0.5MR^2.
where M is the mass of the disc and R is the radius of the disc.
For the axis through the edge, use parallel axis theorem.
I = I(axis through center of mass) + M(distance between the axes)^2
= 0.5MR^2 + MR^2 (since the axis through center of mass is the axis through the center)
= 1.5 MR^2</span>
