Ask question

Ask question

All categories

Svetllana [295]

4 years ago

6

A person with his ear to the ground, sees a huge stone strikethe concrete pavement. A moment later two sounds are heard from the

impact: one travels n the air and the other in the concrete, andthey are 2.2 s apart. How far away did the impact occur?
*The speed of sound for air is 343 m/s, for concrete˜3000.
Please show how you set up the problem and how you got youranswer.

1 answer:

luda_lava [24]4 years ago

7 0

Answer:

852.014 m

Explanation:

The speed of sound in air = 343 m/s = $v_a$

The speed of sound in concrete = 3000 m/s = $v_c$

The distance the sound traveled = s

Time between the sounds heard = 2.2 seconds

Time = Distance / Speed

Time taken by sound travel through air

$\frac{s}{v_a}=\frac{s}{343}$

Time taken by sound travel through concrete

$\frac{s}{v_c}=\frac{s}{3000}$

So,

$\frac{s}{343}-\frac{s}{3000}=2.2\\\Rightarrow \frac{3000s-343s}{1029000}=2.2\\\Rightarrow \frac{2657s}{1029000}=2.2\\\Rightarrow s=\frac{1029000\times 2.2}{2657}\\\Rightarrow s=852.014\ m$

The impact occurs 852.014 m away from the person.

You might be interested in

A hot-air balloon of diameter 12 mm rises vertically at a constant speed of 14 m/s. A passenger accidentally drops his camera fr

fgiga [73]

Answer:

<em>The balloon is 66.62 m high</em>

Explanation:

<u>Combined Motion </u>

The problem has a combination of constant-speed motion and vertical launch. The hot-air balloon is rising at a constant speed of 14 m/s. When the camera is dropped, it initially has the same speed as the balloon (vo=14 m/s). The camera has an upward movement for some time until it runs out of speed. Then, it falls to the ground. The height of an object that was launched from an initial height yo and speed vo is

$\displaystyle y=y_o+v_o\ t-\frac{g\ t^2}{2}$

The values are

$\displaystyle y_o=15\ m$

$\displaystyle v_o=14\ m/s$

We must find the values of t such that the height of the camera is 0 (when it hits the ground)

$\displaystyle y=0$

$\displaystyle y_o+v_o\ t-\frac{g\ t^2}{2}=0$

Multiplying by 2

$\displaystyle 2y_o+2v_ot-gt^2=0$

Clearing the coefficient of $t^2$

$\displaystyle t^2-\frac{2\ V_o}{g}\ t-\frac{2\ y_o}{g}=0$

Plugging in the given values, we reach to a second-degree equation

$\displaystyle t^2-2.857t-3.061=0$

The equation has two roots, but we only keep the positive root

$\displaystyle \boxed {t=3.69\ s}$

Once we know the time of flight of the camera, we use it to know the height of the balloon. The balloon has a constant speed vr and it already was 15 m high, thus the new height is

$\displaystyle Y_r=15+V_r.t$

$\displaystyle Y_r=15+14\times3.69$

$\displaystyle \boxed{Y_r=66.62\ m}$

3 0

3 years ago

Two devices with capacitances of 25 μf and 5.0 μf are each charged with separate 120 v power supplies. calculate the total energ

mash [69]

The energy stored in a capacitor is given by
$U= \frac{1}{2} CV^2$
where C is the value of the capacitance while V is the voltage difference applied to the capacitor.

Let's calculate the energy of the first capacitor:
$U_1 = \frac{1}{2} (25\cdot 10^{-6}F)(120 V)=1.5 \cdot 10^{-3}J$

And now the energy of the second capacitor:
$U_2 = \frac{1}{2} (5 \cdot 10^{-6}F)(120 V)=3 \cdot 10^{-4}J$

So, the total energy stored in the two capacitors is
$U=U_1 +U_2 = 1.8 \cdot 10^{-3}J$

3 0

3 years ago

Read 2 more answers

A train of 150 m length is going toward north direction at a speed of 10 ms–1 and a parrot is flying towards south direction par

zloy xaker [14]

Answer:

10ms

Explanation:

The bird must travel the length of the train (150m), with a combined speed of 15m/s this means it will take 10s to cross an accumulated 150ms.

3 0

4 years ago

Read 2 more answers

56. What is the range of magnitudes that can be attained from the

Svetach [21]

Answer:

Explanation:

Given the magnitude of the forces, 7N and 2N, the minimum combining force acting on the forces are when the force's is acting in opposite direction.

Magnitude of the force in opposite direction is 7N - 5N = 2N

The maximum combining force occurs when they act in the same direction. Magnitude of the force in the same direction is 5N+7N = 12N

Hence the range of magnitude requires is 2N≤F≤12N

8 0

3 years ago

What is the frequency of a pressure wave of wavelength 2.5 m that is traveling at 1400 m/s?

-BARSIC- [3]

The relationship between the speed, the frequency and the wavelength of a wave is given by:
$f= \frac{v}{\lambda}$
where
f is the frequency
v is the speed of the wave
$\lambda$ is its wavelength

for the pressure wave in this problem, $\lambda=2.5 m$ and v=1400 m/s, therefore its frequency is
$f= \frac{v}{\lambda}= \frac{1400 m/s}{2.5 m}=560 Hz$

5 0

3 years ago