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3 years ago

Which substance is a combination of different atoms?

Physics

2 answers:

grigory [225]3 years ago

8 0

Answer:

B. Heterogeneous mixture

Aleks04 [339]3 years ago

8 0

Answer:

It wasn't a heterogeneous mixture, it's compound

Explanation:

I got it wrong on the test when I chose heterogeneous mixture

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Danny sails a boat downstream. The wind pushes the boat along at 21 km/hr. The current runs downstream at 15 km/hr. What is the

abruzzese [7]

Answer:

36 km/h

Explanation:

The total velocity is the sum of the two velocities that add to the movement of the boat.

Since the wind pushes the boat at 21 km/h and the current that runs in the direction of the movent of the boat is 15 km/h, the total velocity at wich the boat moves is:

21km/h + 15 km/h = 36 km/h

3 0

3 years ago

A satellite orbiting the earth is directly over a point on the equator at 12:00 midnight every four days. It is not over that po

Mrrafil [7]

Answer:

106417026.88435 m

Explanation:

T = Time period of the satellite = 4 days

m = Mass of the Earth = 5.972 × 10²⁴ kg

G = Gravitational constant = 6.67 × 10⁻¹¹ m³/kgs²

Time period is given by

$T=2\pi\sqrt{\dfrac{r^3}{GM}}\\\Rightarrow r=\left(\dfrac{T^2GM}{4\pi ^2}\right)^{\dfrac{1}{3}}\\\Rightarrow r=\left(\dfrac{(4\times 24\times 60\times 60)^2\times 6.67\times 10^{-11}\times 5.972\times 10^{24}}{4\pi ^2}\right)^{\dfrac{1}{3}}\\\Rightarrow r=106417026.88435\ m$

The radius of the satellite's orbit is 106417026.88435 m

5 0

3 years ago

What is the current in a wire of radius R = 2.02 mm if the magnitude of the current density is given by (a) Ja = J0r/R and (b) J

Sloan [31]

Explanation:

For this problem we have to take into account the expression

J = I/area = I/(π*r^(2))

By taking I we have

I = π*r^(2)*J

(a)

For Ja = J0r/R the current is not constant in the wire. Hence

$I(r) = \pi r^{2} J(r) = \pi r^{2} J_{0}r/R = \pi r^{3} (3.74*10^{4}A/m^{2})/(2.02*10^{-3}m)$

and on the surface the current is

$I(R) = \pi r^{2} J(R) = \pi r^{2} J_{0}R/R = \pi(2.02*10^{-3})^{2} (3.74*10^{4}) = 0.47 A$

(b)

For Jb = J0(1 - r/R)

$I(r)=\pi r^{2}J(r) =\pi r^{2} J_{0}(1 - r/R)=\pi r^{2}J_{0}(1-\frac{r}{2.02*10^{-3}} )$

and on the surface

$I(R)=\pi r^{2}J_{0}(1-R/R)=\pi r^{2}J_{0}(1-1)= 0$

(c)

Ja maximizes the current density near the wire's surface

Additional point

The total current in the wire is obtained by integrating

$I_{T}=\pi\int\limits^R_0 {r^{2}Ja(r)} \, dr = \pi \frac{J_{0}}{R}\int\limits^R_0 {r^{3}} \ dr =\pi \frac{J_{0}R^{4}}{4R}=\frac{1}{4}\pi J_{0}R^{3}=2.42*10^{-4} A$

and in a simmilar way for Jb

$I_{T}=\pi J_{0} \int\limits^R_0 {r^{2}(1-r/R)} \, dr = \pi J_{0}[\frac{R^{3}}{3}-\frac{R^{2}}{2R}]=\pi J_{0}[\frac{R^{3}}{3}-\frac{R^{2}}{2}]$

And it is only necessary to replace J0 and R.

I hope this is useful for you

regards

7 0

3 years ago

A uniform, solid cylinder of radius 5.00 cm and mass 3.00 kg starts from rest at the top of an inclined plane that is 2.00 m lon

ch4aika [34]

To solve this problem we will apply the principle of conservation of energy, for which the initial potential and kinetic energy must be equal to the final one. The final kinetic energy will be transformed into rotational and translational energy, so the mathematical expression that approximates this deduction is

KE_i+PE_i = KE_{trans}+KE_{rot} +PE_f

$KE_i = 0$ , since initially cylinder was at rest

$PE_f = 0$ since at the ground potential energy is zero

The mathematical values are,

$mgh = \frac{1}{2} mV^2 + \frac{1}{2}I\omega^2$

Here,

m = mass

g= Gravity

h = Height

V = Velocity

$I = \frac{mr^2}{2}$ moment of Inertia in terms of its mass and radius

$\omega = \frac{V}{r}$ Angular velocity in terms of tangential velocity and its radius

Replacing the values we have that

mgh = \frac{1}{2} mv^2 +\frac{1}{2} (\frac{mr^2}{2})(\frac{v}{r})^2

gh = \frac{v^2}{2}+\frac{v^2}{4}

v = \sqrt{\frac{4gh}{3}}

From trigonometry the vertical height of inclined plane is the length of this plane for $sin\theta$ , then

$h = 2.00*sin 25$

$h = 0.845 m$

Replacing,

$v = \sqrt{\frac{4(9.8)(0.845)}{3}}$

$V = 3.32 m/s$

Therefore the cylinder's speedat the bottom of the ramp is 3.32m/s

6 0

3 years ago

If the fundamental frequency of a musical instrument is 42Hz, what is the frequency of the second harmonic?

timurjin [86]

For the majority of instruments f = n f0 where f is the resonating frequency, n is any whole number and f0 is the fundamental.
This applies to trumpets, violins, flutes and a broad range. 
In such a case the first harmonic would be at n=1 and the second harmonic would be at n=2 

which gives a frequency of 84 Hz

7 0

3 years ago