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3 years ago

Which of the following frequencies falls in the range of RF waves used by commercial radio broadcasting stations?

Physics

2 answers:

dybincka [34]3 years ago

8 0

A. 6,000,000 Hz =3 they were correct

shusha [124]3 years ago

8 0

It's D. 600,000 Hz

I just took the test :)

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Give a real life example in which two objects are moving at a constant speed but have different velocities.

Bad White [126]

Answer:

The planets and moons that orbit in the solar system.

Explanation:

For example the earth moves at 67,000 mph (107,000 km/h), and is constant from the gravitational pull of the sun. The moon orbits at about 2,288 mph (3,683 km/h). these are both traveling at different velocities but at a constant speed.

6 0

2 years ago

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5. Graph A plots a race car's speed for 5 seconds. The car's

Nastasia [14]

The answer for the cars speed is tue

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2 years ago

You attach a 3.10 kg weight to a horizontal spring that is fixed at one end. You pull the weight until the spring is stretched b

dolphi86 [110]

Answer:

0.785 m/s

Explanation:

Hi!

To solve this problem we will use the equation of motion of the harmonic oscillator, i.e.

$x(t) = A cos(\omega t )+B sin(\omega t)$ - (1)

$\frac{dx}{dt}(t) = \omega (B cos(\omega t )- A sin(\omega t)$ - (1)

The problem say us that the spring is released from rest when the spring is stretched by 0.100 m, this condition is given as:

$x(0) = 0.100$

$\frac{dx}{dt}(0) = 0$

Since cos(0)=1 and sin(0) = 0:

$x(0)=A$

$\frac{dx}{dt}(0) = -B\omega$

We get

$A =0.100\\B = 0$

Now it say that after 0.4s the weigth reaches zero speed. This will happen when the sping shrinks by 0.100. This condition is written as:

$x(0.4) = - 0.100$

Since

$x(t) = 0.100 cos(\omega t)\\ -0.100=x(0.4)=0.100cos(\omega 0.4)$

This is the same as:

$-1 = cos(0.4\omega)$

We know that cosine equals to -1 when its argument is equal to:

(2n+1)π

With n an integer

The first time should happen when n=0

Therefore:

π = 0.4ω

ω = π/0.4 -- (2)

Now, the maximum speed will be reached when the potential energy is zero, i.e. when the sping is not stretched, that is when x = 0

With this info we will know at what time it happens:

$0 = x(t) = 0.100cos(\omega t)$

The first time that the cosine is equal to zero is when its argument is equal to π/2

i.e.

$t_{maxV}=\pi /(2\omega)$

And the velocity at that time is:

$\frac{dx}{dt}(t_{maxV} ) =- 0.100\omega sin(\omega t_{maxV})\\\frac{dx}{dt}(t_{maxV} ) =- 0.100\omega sin(\pi/2)\\$

But sin(π/2) = 1.

Therefore, using eq(2):

$\frac{dx}{dt}(t_{maxV} ) = 0.100*\omega = 0.100\frac{\pi}{0.400} = \pi/4$

And so:

$V_{max} = \pi / 4 =0.785$

6 0

2 years ago

A 50kg girl is playing soccer. She runs towards the ball at a speed of 7 m/s. How much kinetic energy does she have as she runs

stepladder [879]

The calculation for kinetic energy is this

KE = 1/2mv^2

KE = 1/2(50)(7^2)

KE = 1/2(49•50)

KE = 1225 kgm^2/s^2.

Or simply 1225 J.

She possess this much energy when she runs.

3 0

3 years ago

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A 1.11 kg piece of aluminum at 78.3 c is put into a glass with 0.210 kg of water at 15.0

ValentinkaMS [17]

M = mass of aluminium = 1.11 kg

$c_{a}$ = specific heat of aluminium = 900