How to reduce fluid friction

One person is in a pool and is diving to a depth of 2.3m, and another person is diving to a depth of 3m. What pressure does each

Vlad [161]

Explanation:

The static pressure is P = ρgh, where ρ is the density of the fluid and h is the depth.

For the first person:

P = (1000 kg/m³) (9.8 m/s²) (2.3 m)

P = 22,500 Pa

For the second person:

P = (1000 kg/m³) (9.8 m/s²) (3 m)

P = 29,400 Pa

6 0

3 years ago

A 210-kg woorden raft floats on a lake. When a 75-kg man stands on the raft, it sinks 5.0 cm deeper into the water. When he step

GaryK [48]

Answer:

A: The frequency of the vibration is 1.3329 Hz

B: The total energy of the vibration is 18.39375 J

Explanation:

The force of the man his weight causes the raft to sink, and that causes the water to put a larger upward force on the raft. This extra force is a restoring force, because it is in the opposite direction of the force put on the raft by the man. Then when the man steps off, the restoring force pushes upward on the raft, and thus the raft – water system acts like a spring, with a spring constant found as follows:

k= F/x = ((75 kg) * (9.81 m/s²))/(5*10^-2 m) = 14715 N/m

The frequency of the vibration is determined by the spring constant (k) and the mass of the raft (210kg).

fn = 1/2π * √(k/m) = 1/2π * √(14715 / 210) = 1.3329 Hz

The frequency of the vibration is 1.3329 Hz

b)

Since the gravitational potential energy can be ignored, the total energy will be :

Etot = 1/2 k* A² = 1/2 * (14715 )*(0.05)² = 18.39375 J

The total energy of the vibration is 18.39375 J

7 0

2 years ago

The following table lists the work functions of a few commonmetals, measured in electron volts.

steposvetlana [31]

Answer:

Lithium

Explanation:

The equation for the photoelectric effect is

$\frac{hc}{\lambda}= \phi + K_{max}$

where

$\frac{hc}{\lambda}$ is the energy of the incident photon, with

h being the Planck constant

c is the speed of light

$\lambda$ is the wavelength of the photon

$\phi$ is the work function of the metal (the minimum energy needed to extract the photoelectron from the metal)

$K_{max}$ is the maximum kinetic energy of the emitted photoelectrons

In this problem, we have

$\lambda= 190 nm = 1.9\cdot 10^{-7}m$ is the wavelength of the incident photon

$K_{max}=4.0 eV$ is the maximum kinetic energy of the electrons

First of all we can find the energy of the incident photon

$E=\frac{(6.63\cdot 10^{-34} Js)(3\cdot 10^8 m/s)}{1.90\cdot 10^{-7} m}=1.05\cdot 10^{-18} J$

Converting into electronvolts,

$E=\frac{1.05\cdot 10^{-18} J}{1.6\cdot 10^{-19} J/eV}=6.6 eV$

So now we can re-arrange the equation of the photoelectric effect to find the work function of the metal

$\phi = E-K_{max}=6.6 eV - 4.0 eV=2.6 eV$

So the metal is most likely Lithium, which has a work function of 2.5 eV.

3 0

3 years ago

The aorta is approximately 25 mm in diameter. The mean pressure there is about 100 mmHg and the blood flows through the aorta at

Ksenya-84 [330]

Answer:

Explanation:

25 mm diameter

r₁ = 12.5 x 10⁻³ m radius.

cross sectional area = a₁

Pressure P₁ = 100 x 10⁻³ x 13.6 x 9.8 Pa

a )

velocity of blood v₁ = .6 m /s

Cross sectional area at blockade = 3/4 a₁

Velocity at blockade area = v₂

As liquid is in-compressible

a₁v₁ = a₂v₂

a₁ x .6 m /s = 3/4 a₁ v₂

v₂ = .8m/s

b )

Applying Bernauli's theorem formula

P₁ + 1/2 ρv₁² = P₂ + 1/2 ρv₂²

100 x 10⁻³ x 13.6 x10³x 9.8 + 1/2 X 1060 x .6² = P₂ + 1/2x 1060 x .8²

13328 +190.8 = P₂ + 339.2

P₂ = 13179.6 Pa

= 13179 / 13.6 x 10³ x 9.8 m of Hg

P₂ = .09888 m of Hg

98.88 mm of Hg

8 0

3 years ago

If a conducting loop of radius 10 cm is onboard an instrument on Jupiter at 45 degree latitude, and is rotating with a frequency

Pepsi [2]

Answer:

a) fem = - 2.1514 10⁻⁴ V, b) I = - 64.0 10⁻³ A, c) P = 1.38 10⁻⁶ W

Explanation:

This exercise is about Faraday's law

fem = $- \frac{ d \Phi_B}{dt}$

where the magnetic flux is

Ф = B x A

the bold are vectors

A = π r²

we assume that the angle between the magnetic field and the normal to the area is zero

fem = - B π 2r dr/dt = - 2π B r v

linear and angular velocity are related

v = w r

w = 2π f

v = 2π f r

we substitute

fem = - 2π B r (2π f r)

fem = -4π² B f r²

For the magnetic field of Jupiter we use the equatorial field B = 428 10⁻⁶T

we reduce the magnitudes to the SI system

f = 2 rev / s (2π rad / 1 rev) = 4π Hz

we calculate

fem = - 4π² 428 10⁻⁶ 4π 0.10²

fem = - 16π³ 428 10⁻⁶ 0.010

fem = - 2.1514 10⁻⁴ V

for the current let's use Ohm's law

V = I R

I = V / R

I = -2.1514 10⁻⁴ / 0.00336

I = - 64.0 10⁻³ A

Electric power is

P = V I

P = 2.1514 10⁻⁴ 64.0 10⁻³

P = 1.38 10⁻⁶ W

6 0

2 years ago