A train whistle is heard at 350 Hz as the train approaches town. The train cuts its speed in half as it nears the station, and t
1 answer:
Answer:
(a). 19.0 m/s
(b). 9.5m/s
Explanation:
Assuming speed of sound is 343m/s.
(a).
As the train approaches, from the the Doppler equation we have
solving for we get:
.
And as the train cuts its speed in half, the equation gives
substituting the value of we get:
or 68.6 km per hour, which is the speed of the train before slowing down.
(b).
The speed of the train after slowing down is half the previous speed; therefore,
or 34.3 km per hour.
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Answer:
The current in the coil is 4.086 A
Explanation:
Given;
radius of the circular coil, R = 2.5 cm = 0.025 m
number of turns of the circular coil, N = 740 turns
magnetic field at the center of the coil, B = 0.076 T
The magnetic field at the center of the coil is given by;
where;
μ₀ is permeability of free space = 4 x 10⁻⁷ m/A
I is the current in the coil
R is radius of the coil
N is the number of turns of the coil
The current in the circular coil is given by
Therefore, the current in the coil is 4.086 A
Answer:
It will still hover until the spaceship "hits" or exerts a force on it.
Explanation:
Remember, if there is no net force, there is no acceleration or movement.
In this case, our ball is hovering in the spaceship, and in space, we can assume there is no , and we can assume there is no
, nor no forces acting against it.
So, the ball would not move.
However, once the spaceship starts accelerating, the ball would still hover until the spaceship exerts a force on it.
This is because of the same thing as explained above, no forces acting on it, therefore, no acceleration.
Think about it this way.
Imagine you jumped up, then someone threw a ball at you. Now let's imagine you can't move until you hit the floor, meaning that in an ideal situation only is acting on you. Now again, let's imagine time slows really down for you, but not the ball. Before the ball comes and hits you, you are "hovering" like a ball. But after the ball hits you, you move a little because the ball exerted a force on you.
If you did not understand what I meant above, just forget about it, and think about the fact that if there is a Net force (all the force values added up), then there is acceleration and movement.