Energy. (4 points)

What type of change occurs when water change from a solid to a iquid?

Oksanka [162]

The type of change is melting

6 0

3 years ago

A car approaches you at a constant speed, sounding its horn, and you hear a frequency of 76 Hz. After the car goes by, you hear

Talja [164]

Answer:

70.07 Hz

Explanation:

Since the sound is moving away from the observer then

$f_o = f_s\frac {(v+vs)}{v}$ and $f_o = f_s\frac {(v-vs)}{v}$ when moving towards observer

With $f_o$ of 76 then taking speed in air as 343 m/s we have

$76 = f_s\times\frac {(343-vs)}{343}$

$f_s=\frac {343\times 76}{343-v_s}$

Similarly, with $f_o$ of 65 we have

$65 = f_s\times\frac {(343+vs)}{343}\\f_s=\frac {343\times 65}{343+v_s}$

Now

$f_s=\frac {343\times 65}{343+v_s}=\frac {343\times 76}{343-v_s}$

v_s=27.76 m/s

Substituting the above into any of the first two equations then we obtain

$f_s=70.07 Hz$

4 0

3 years ago

By how much will the velocity of a vehicle change if it accelerates at 10 m/s/s for a period of 10 seconds

pishuonlain [190]

Answer:

Explanation:

we know that the time rate of change of velocity is called acceleration mathmetically;

a=Δv/Δt

Δv=a*Δt

a=10 m/s²

t=10 sec

Δv=10*10=100 m/s

7 0

4 years ago

Which of these biomes receives the least amount of rainfall every year?

ASHA 777 [7]

Answer:

Desert

Explanation:

The desert receives the least amount of rainfall yearly.

A desert can be described a barren area of land where little amount of rainfall occurs and, because of this, living conditions are not favourable for plants and animal life. Because there is no vegetation in a desert, the bare surface of the ground are subjected to denudation.

5 0

3 years ago

The beautiful Multnomah Falls in Oregon are approximately 206m high. If the Columbia river is flowing horizontally at 2.90m/s ju

zhenek [66]

Answer:

The overall velocity of the water when it hits the bottom is:

$v_f=63.61\ \frac{m}{s}$

Explanation:

Use the law of conservation of energy.

Call it instant [1] to the moment when the water is just before reaching the falls.

At this moment its height h is 206 meters and its velocity horizontally $v_i$ is $v_i = 2.90$ m/s.

At the instant [1] the water has gravitational power energy $E_g$

$E_g = mgh$

The water also has kinetic energy Ek.

$E_k = 0.5mv_i ^ 2$

Then the Total E1 energy is:

$E_1 = mgh + 0.5mv_i ^ 2$

In the instant [2] the water is within an instant of touching the ground. At this point it only has kinetic energy, since the height h = 0. However at time [2] the water has maximum final velocity $v_f$

So:

$E_2 = 0.5mv_f ^ 2$

As the energy is conserved then $E_1 = E_2$

$mgh + 0.5mv_i ^ 2 = 0.5mv_f ^ 2$

Now we solve for $v_f$ .

$gh + 0.5v_i ^ 2 = 0.5v_f ^ 2\\\\9.8(206) + 0.5(2.90) ^ 2 = 0.5v_f 2\\\\v_f^2 = \frac{9.8(206) + 0.5(2.90) ^ 2}{0.5}\\\\v_f = \sqrt{\frac{9.8(206) + 0.5(2.90) ^ 2}{0.5}}\\\\v_f=63.61\ \frac{m}{s}$

7 0

3 years ago