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3 years ago

What happens to the sound of a train whistle as a train approaches and passes you? Why?

1 answer:

7 0

When. the train approaches you, the wavelength of the sound waves it emits are compressed, and therefore the whistle sounds higher.

But When the train is moving away, the wavelengths are extended, causing the whistle to sound lower. It's called the Doppler effect.

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A Cessna aircraft has a liftoff speed of 120 km/h What minimum constant acceleration does the aircraft require to be airborne af

Lady_Fox [76]

Answer:

Explanation:

Using the equation of motion v² = u²+2aS

v is the final velocity = 120km/hr

120km/hr = 120 * 1000/1 * 3600 = 33.3m/s

u is the initial velocity = 0m/s

a is the acceleration

S is the distance covered = 240m

On substituting the given parameters

33.3² = 0²+2a(240)

33.3² = 480a

1110 = 480a

a = 1110/480

a = 2.3125m/s²

Hence the minimum constant acceleration that the aircraft require to be airborne after a takeoff run of 240 m is 2.3125m/s²

4 0

4 years ago

The United States and South Korean soccer teams are playing in the first round of the World Cup. An American kicks the ball, giv

Aleks04 [339]

Answer:v=2.82 m/s

Explanation:

Given

initial velocity of ball(u)=3.6 m/s

ball rolls a distance(s) of 5 m

ball acceleration $=-0.5 m/s^2$

Velocity of ball when it is intercepted by Korean player

$v^2-u^2=2as$

$v^2=3.6^2+2(-0.5)(5)=7.96$

$v=\sqrt{7.96}$

$v=2.82 m/s$

3 0

3 years ago

Which type of electromagnetic radiation cannot be focused?

Irina18 [472]

The answer is A. Hope this helps. :)

7 0

3 years ago

Read 2 more answers

What is the source of all mechanical waves?

igor_vitrenko [27]

The answer is vibration

6 0

3 years ago

Read 2 more answers

You stretch a spring by a distance of 0.3 m. The spring has a spring constant of 440 N/m. When you release the spring, it snaps

QveST [7]

The kinetic Energy has to be the same as the Energy with which the spring was stratched:
1/2×m×v^2=1/2×D×s^2
Ekin=1/2×440×0.3^2= 1/2×440×0.09=19.8. ( Of course, the kinetic Energy is normally Not calculated Like this , but in this case both Formulas have the Same solution so you can Wright it Like This)
By the way, if the spring Had Not reached its Natural length yet, you wouldnt be right if you calculate it Like above, because a Part of the Energy is still in the spring : Espring=Ekin+Espring2

3 0

4 years ago