Divergent plate boundaries are when plates

A computer hard disk starts from rest, then speeds up with an angular acceleration of 190 rad/s2rad/s2 until it reaches its fina

Otrada [13]

Answer:

962 rpm.

Explanation:

given,

angular acceleration = 190 rad/s²

initial angular speed = 0 rad/s

final angular speed = 7200 rpm

= $7200\times\dfrac{2\pi}{60}$

= $754\ rad/s$

we need to calculate the revolution of disk after 10 s.

time taken to reach the final angular velocity

using equation of angular motion

$\omega_f - \omega_i = \alpha t$

$754 - 0 =190\times t$

t = 4 s

rotation of wheel in 4 s

$\theta =\omega_i t+ \dfrac{1}{2}\alpha t$

$\theta = \dfrac{1}{2}\alpha t^2$

$\theta = \dfrac{1}{2}\times 190 \times 4^2$

θ = 1520 rad

$\theta = \dfrac{1520}{2\pi}$

$\theta =242\ rev$

now, revolution of the disk in next 6 s

angular velocity is constant

$\omega_f = \dfrac{\theta_f-\theta_i}{t_f-t_i}$

$754 = \dfrac{\theta_f-1520}{10-4}$

θ_f = 6044 rad

θ_f = $\dfrac{6044}{2\pi}$

revolution of the computer hard disk

θ_f = 962 rpm.

total revolution of the computer disk after 10 s is equal to 962 rpm.

3 0

3 years ago

Contact lenses are designed to be gas permeable in order to allow oxygen to diffuse to the eye. If the edge of a contact lens is

guapka [62]

Answer: A

The diffusion time through the edge is double the diffusion time through the center.

Explanation:

Only the diffusion coefficient, thickness, surface area, distance affects the time it takes a gas such as oxygen to diffuse a given in a medium. The Diffusion time increases with the square of diffusion distance Also, the Increased surface area increases the rate of diffusion or the diffusion time, whereas a thicker membrane reduces the rate of diffusion or time it takes the gas to be permeable. Also, The greater the distance that a substance must travel, the slower the rate of diffusion The diffusion coefficient determines the time it takes a gas to diffuse. Also the Diffusion time is inversely proportional to the diffusion coefficient.

Now, If the edge of a contact lens is double the thickness of the central portion of the lens, then it will take more time for the gas to diffuse through the thicker portion. since its edge is double the central position, then the diffusion time will also be doubled. So Option A is the best answer-

The diffusion time through the edge is double the diffusion time through the center.

6 0

4 years ago

What effect do impurities have on the crystal lattice? Why does that result in the lowering of the melting point of a solid?

s344n2d4d5 [400]

Answer:

It reduces the melting point due to a defect in the arrangement of the crystal lattice.

Explanation:

The presence of impurities creates a disorderliness in the uniformity of the crystal structure. It lowers the melting point by a few degrees because it becomes easier to overcome the intermolecular force of attraction.

It makes the array of crystals disordered.

Lattice is a long chain three-dimensional arrangement of the molecules, atoms or ions in a crystal structure.

3 0

4 years ago

The basal metabolic rate is the rate at which energy is produced in the body when a person is at rest. A 75-kg (165-lb) person o

CaHeK987 [17]

Answer:

(a) Q = 142.67 W

(b) Basal Metabolic Rate = 178.33 W

Explanation:

(a)

We can find the heat radiated by the person by using Stefan-Boltzman's law:

$Q = \sigma A (T^4 - T_{s}^4)\\$

where,

Q = heat radiated per second = ?

σ = Stefan-Boltzman Constant = 5.6703 x 10⁻⁸ W/m².k⁴

A = Surface Area = 2 m²

T = Temperature of Skin = 30° C + 273 = 303 k

Ts = Temperature of room = 18° C +273 = 291 k

Therefore,

$Q = (5.6703\ x\ 10^{-8}\ W/m^2.k^4)(2\ m^2)[(303\ k)^4-(291\ k)^4]$

Q = 142.67 W

(b)

Since the heat calculated in part (a) is 80 percent of basal metabolic rate. Therefore,

$Q = (0.8)(Basal\ Metabolic\ Rate)\\Basal\ Metabolic\ Rate = \frac{Q}{0.8}\\\\Basal\ Metabolic\ Rate = \frac{142.67\ W}{0.8}$

Basal Metabolic Rate = 178.33 W

5 0

3 years ago

What is the energy of photons emitted by the led at a frequency of 610 thz mcat?

Ksju [112]

The photon energy is the energy carried by a single proton.

The equation used for calculating photon energy is:

E = hc / λ

where h = Planck constant

c = speed of light and

λ = wavelength of photon

frequency = f = c / λ

replace c /λ with f in the equation of photon energy

E = hf

frequency = 610 thz = 6.1 x 10¹⁴hz

h = 6.26 x 10⁻³⁴ js

E = 6.26 x 10⁻³⁴ x 6.1 x 10¹⁴

E = 3.8 x 10⁻¹⁹ j

4 0

3 years ago