Answer:

Explanation:
First, we write the equations of motion for each axis. Since the crate is sliding with constant speed, its acceleration is zero. Then, we have:

Where T is the tension in the rope, F is the force exerted by the first worker, f_k is the frictional force, N is the normal force and mg is the weight of the crate.
Since
and
, we can rewrite the first equation as:

Now, we solve for
and calculate it:

This means that the crate's coefficient of kinetic friction on the floor is 0.18.
Both the effects (l<span>engthening of the transmitted signal's wavelength and decrease in its frequency) indicates that the object is moving away from the observer, and this phenomenon is called Doppler effect.
In fact, when the object is moving away from the observer, the relative distance between two consecutive crests of the wave emitted by the object increases to the observer eyes, since he's moving away. This means that the wavelength appears larger, and since the frequency is inversely proportional to the wavelength, the frequency appears smaller.</span>
Answer:
0.196 m
Explanation:
Given in the question that,
time taken by the dolphin to go back to water = 0.2 sec
To solve the question we will use Newton's Law of motion
<h3>S = ut + 0.5(a)t²</h3>
here S is distance covered
u is initial speed
a = acceleration due to gravity
t = time taken
Plug value in the equation above
S = 0(0.2) + 0.5(-9.8)(0.2)²
S = 0.5(-9.8)(0.2)²
S = -0.196 m
Negative sign represent direction
(Assuming that dolphin have a vertical straight jump not a projectile motion)
Answer:
usually x-ray tube filaments are devices that limit the current flow i.e. current cannot easily pass through them or we can say that they are current limited devices. So to allow fine electron transmission control by filament heating current, rhenium must not be used in x-ray tube filaments.
Answer: b. infrared
Explanation:
The visible light with the smaller frequency is associated with the color red.
While the blue is the one with the larger frequency.
Now, as the name says, infrared waves are the ones with a frequency just below the one of the red visible light.
Where the frequency of the red light is something around (4.3*10^14 Hz)
and the frequency of the infrared waves is in the range between (10^12 Hz and 10^14 Hz)
Then the correct option is b, infrared.