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3 years ago

A baseball player throws 4 balls every 20 seconds. what is his throw frequency

Physics

1 answer:

frosja888 [35]3 years ago

3 0

Answer:

Frequency, f = 0.2 Hz

Explanation:

We have,

A baseball player throws 4 balls every 20 seconds.

It is required to find the frequency of the baseball.

Frequency of an object is defined as the number of times an event occurs. It is given by number of throws per unit time. It can be given by :

$f=\dfrac{4}{20}\\\\f=0.2\ Hz$

So, the frequency of his throw is 0.2 Hz.

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Cobalt

Explanation:

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A distant large asteroid is detected that might pose a threat to Earth. If it were to continue moving in a straight line at cons

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Answer:

The minimum speed required is 5.7395km/s.

Explanation:

To escape earth, the kinetic energy of the asteroid must be greater or equal to its gravitational potential energy:

$K.E\geq P.E$

$\dfrac{1}{2}mv^2 \geq G\dfrac{Mm}{R}$

where $m$ is the mass of the asteroid, $R= 24,000,000\:m$ is its distance form earth's center, $M = 5.9*10^{24}kg$ is the mass of the earth, and $G = 6.7*10^{-11}m^3/kg\: s^2$ is the gravitational constant.

Solving for $v$ we get:

$v \geq \sqrt{\dfrac{2GM}{R} }$

putting in numerical values gives

$v \geq \sqrt{\dfrac{2(6.7*10^{-11})(5.9*10^{24})}{(24,000,000)} }$

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in kilometers this is

$v\geq5.7395m/s.$

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3 years ago

A particle initially located at the origin has an acceleration of vector a = 2.00ĵ m/s2 and an initial velocity of vector v i =

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With acceleration

$\mathbf a=\left(2.00\dfrac{\rm m}{\mathrm s^2}\right)\,\mathbf j$

and initial velocity

$\mathbf v(0)=\left(8.00\dfrac{\rm m}{\rm s}\right)\,\mathbf i$

the velocity at time t (b) is given by

$\mathbf v(t)=\mathbf v(0)+\displaystyle\int_0^t\mathbf a\,\mathrm du$

$\mathbf v(t)=\left(8.00\dfrac{\rm m}{\rm s}\right)\,\mathbf i+\displaystyle\int_0^t\left(2.00\dfrac{\rm m}{\mathrm s^2}\right)\,\mathbf j\,\mathrm du$

$\mathbf v(t)=\left(8.00\dfrac{\rm m}{\rm s}\right)\,\mathbf i+\left(2.00\dfrac{\rm m}{\mathrm s^2}\right)u\,\mathbf j\bigg|_{u=0}^{u=t}$

$\mathbf v(t)=\left(8.00\dfrac{\rm m}{\rm s}\right)\,\mathbf i+\left(2.00\dfrac{\rm m}{\mathrm s^2}\right)t\,\mathbf j$

We can get the position at time t (a) by integrating the velocity:

$\mathbf x(t)=\mathbf x(0)+\displaystyle\int_0^t\mathbf v(u)\,\mathrm du$

The particle starts at the origin, so $\mathbf x(0)=\mathbf0$ .

$\mathbf x(t)=\displaystyle\int_0^t\left(8.00\dfrac{\rm m}{\rm s}\right)\,\mathbf i+\left(2.00\dfrac{\rm m}{\mathrm s^2}\right)u\,\mathbf j\,\mathrm du$

$\mathbf x(t)=\left(\left(8.00\dfrac{\rm m}{\rm s}\right)u\,\mathbf i+\dfrac12\left(2.00\dfrac{\rm m}{\mathrm s^2}\right)u^2\,\mathbf j\right)\bigg|_{u=0}^{u=t}$

$\mathbf x(t)=\left(8.00\dfrac{\rm m}{\rm s}\right)t\,\mathbf i+\left(1.00\dfrac{\rm m}{\mathrm s^2}\right)t^2\,\mathbf j$

Get the coordinates at t = 8.00 s by evaluating $\mathbf x(t)$ at this time:

$\mathbf x(8.00\,\mathrm s)=\left(8.00\dfrac{\rm m}{\rm s}\right)(8.00\,\mathrm s)\,\mathbf i+\left(1.00\dfrac{\rm m}{\mathrm s^2}\right)(8.00\,\mathrm s)^2\,\mathbf j$

$\mathbf x(8.00\,\mathrm s)=(64.0\,\mathrm m)\,\mathbf i+(64.0\,\mathrm m)\,\mathbf j$

so the particle is located at (x, y) = (64.0, 64.0).

Get the speed at t = 8.00 s by evaluating $\mathbf v(t)$ at the same time:

$\mathbf v(8.00\,\mathrm s)=\left(8.00\dfrac{\rm m}{\rm s}\right)\,\mathbf i+\left(2.00\dfrac{\rm m}{\mathrm s^2}\right)(8.00\,\mathrm s)\,\mathbf j$

$\mathbf v(8.00\,\mathrm s)=\left(8.00\dfrac{\rm m}{\rm s}\right)\,\mathbf i+\left(16.0\dfrac{\rm m}{\rm s}\right)\,\mathbf j$

This is the velocity at t = 8.00 s. Get the speed by computing the magnitude of this vector:

$\|\mathbf v(8.00\,\mathrm s)\|=\sqrt{\left(8.00\dfrac{\rm m}{\rm s}\right)^2+\left(16.0\dfrac{\rm m}{\rm s}\right)^2}=8\sqrt5\dfrac{\rm m}{\rm s}\approx17.9\dfrac{\rm m}{\rm s}$

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2 years ago

If an atom has 34 protons and 40 neutrons, what is its atomic number?

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The atomic number is 34. (A)

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3 years ago

Read 2 more answers

If diameter and length of a cylinder are 0.01 m and 0.07 m respectively, the thermal conductivity of air is 0.028 W/mK and the N

kap26 [50]

Answer:

The convective heat transfer coefficient of the fluid is 170.4 watts per square meter-degree Celsius.

Explanation:

The Nusselt number ( $Nu$ ) is a dimensionless factor which compares the sensitivity of a fluid due to convection with those due to conduction:

$Nu = \frac{h\cdot L_{c}}{k}$ (Eq. 1)

Where:

$h$ - Convective heat transfer coefficient, measured in watts per square meter-degree Celsius.

$k$ - Conductive heat transfer coefficient, measured in watts per meter-degree Celsius.

$L_{c}$ - Characteristic length, measured in meters.

In addition, the characteristic length of a cylinder is defined by the following formula:

$L_{c} = \frac{\pi\cdot r^{3}\cdot l}{2\pi\cdot r^{2}+2\pi\cdot r \cdot l}$ (Eq. 2)

Where:

$r$ - Radius of the cylinder, measured in meters.

$l$ - Length of the cylinder, measured in meters.

If we know that $Nu = 14.2$ , $k = 0.028\,\frac{W}{m\cdot ^{\circ}C}$ , $r = 0.005\,m$ and $l = 0.07\,m$ , then the convective heat coefficient is:

From (Eq. 2):

$L_{c} = \frac{\pi\cdot (0.005\,m)^{2}\cdot (0.07\,m)}{2\pi\cdot (0.005\,m)^{2}+2\pi\cdot (0.005\,m)\cdot (0.07\,m)}$

$L_{c} = \frac{7}{3000}\,m$

And by (Eq. 1):

$h = \frac{k\cdot Nu}{L_{c}}$

$h = \frac{\left(0.028\,\frac{W}{m\cdot ^{\circ}C} \right)\cdot (14.2)}{\frac{7}{3000}\,m }$

$h = 170.4\,\frac{W}{m^{2}\cdot ^{\circ}C}$

The convective heat transfer coefficient of the fluid is 170.4 watts per square meter-degree Celsius.

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2 years ago