You have a 40-Hz sound wave and a 5,000-Hz sound wave. Both are traveling
1 answer:
Answer:
Both sound waves will travel at the same speed.
Explanation:
The speed of sound depends only on the density and the elastic properties of the medium it is travelling through, the mathematical relation is
,
where is the bulk modulus<em> (a measure of how much a material will compress under a certain pressure)</em>, and
is the density of the medium.
Since the frequency of a sound wave does not change the properties of the medium it is travelling through, every frequency will have the same speed through a certain medium.
Hence, a 5,000 Hz and a 40-Hz sound wave will have the same speed through steel.
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A) 2.64 H
The maximum height that the expelled rock can reach can be found by using the equation:
where
v = 0 is the velocity at the maximum height
u is the initial velocity
g is the acceleration of gravity
d is the maximum height
Solving for d,
We see that the maximum heigth is inversely proportional to g. On the Earth,
and
So we can write:
where H' is the maximum height reached on Mars, and is the acceleration of gravity on Mars. Solving for H',
B) 2.64T
The time after which the rock reaches the maximum height can be found by using
where
v = 0 is the velocity at the maximum height
u is the initial velocity
Solving for t,
The total time of the motion is twice this value, so:
So we see that it is inversely proportional to g.
On the Earth, t = T. So we can write:
where T' is the total time of the motion on Mars. Solving for T',
Answer:
The books slide to the left due to inertia, and then they come to a rest due to the force applied by the car door.
Explanation:
The entire motion of the books can be explained by using the first two laws of Newton:
- 1st Newton's law (also called Law of Inertia): an object at rest stays at rest and an object in motion stays in motion with constant velocity if no unbalanced forces act on it
- 2nd Newton's law: when an object is acted upon unbalanced forces, an acceleration is induced in the motion of the object, according to the equation
where F is the net force on the object, m is its mass and a is its acceleration.
Coming back to our problem:
- At the beginning, Argelia makes a sharp turn right. Due to the law of inertia, the books (which are not fixed to the car) continue their motion straight as it was before the curve: so, since the car is moving right, they appear to go the left of the car.
- When the books hit the car door, they stop moving due to the 2nd Newton's law: in fact, the car door applies an unbalanced force against the books, and as a result the books have a negative acceleration (=deceleration), so they slow down and eventually they stop.