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4 years ago

What are the eight levels of classification in order

1 answer:

4 0

The Levels of Classification. Every organism can be classifiedat 7 different levels - kingdom, phylum, class, order, family, genus and species. Each level contains organisms with similar characteristics. The kingdom is the largest group and very broad

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In the above diagram, the block is at static equilibrium on the ground. What is the value of the force exerted by the ground on

Liula [17]

Answer: C. -12 newtons

Explanation: Since, the block is in static equilibrium,

the net force on the block is zero i.e. balance forces are acting on the block.

In the horizontal direction,

force applied+force due to friction = 0

20 N + (-20N) = 0

In the vertical direction as well, net force is zero:

Force due to gravity + force exerted by the ground = 0

12 N + force exerted by the ground = 0

⇒force exerted by the ground = 0 -12 N = -12 N

Thus, the correct option is C. -12 N where negative sign means that the direction of the force due to ground is opposite to the force of gravity.

8 0

3 years ago

A proton of mass mp is released from rest just above the lower plate and reaches the top plate with speed vp. An electron of mas

vodka [1.7K]

Answer:

$v_e=\sqrt{\frac{m_pv_p^2}{m_e}}$

Explanation:

You can consider that the force that acts over the proton is the same to the force over the electron. This is because the electric force is given by:

$F=qE$

$F_p=F_e$

where E is the constant electric field between the parallel plates, and is the same for both electron and proton. Also, the charge is the same.

by using the Newton second law for the proton, and by using kinematic equation for the calculation of the acceleration you can obtain:

$m_pa_p=qE\\\\a_p=\frac{v_p^2}{2d}\\\\\frac{m_pv_p^2}{2d}=qE$

(it has been used that vp^2 = v_o^2+2ad) where d is the separation of the plates, ap the acceleration of the proton, vp its velocity and mp its mass.

By doing the same for the electron you obtain:

$\frac{m_ev_e^2}{2d}=qE$

we can equals these expressions for both proton and electron, because the forces qE are the same:

$\frac{m_pv_p^2}{2d}=\frac{m_ev_e^2}{2d}\\\\v_e=\sqrt{\frac{m_pv_p^2}{m_e}}$

4 0

4 years ago

A certain metal with work function of Φ = 1.7 eV is illuminated in vacuum by 1.4 x 10-6 W of light with a wavelength of λ = 600

Makovka662 [10]

Answer:

1) n = 4.47*10^12 photons

2) K = 0.25 eV

Explanation:

This is a problem about the photoelectric effect.

1) In order to calculate the number of photons that impact the metal, you take into account the power of the light, which is given by:

$P=\frac{E}{t}=1.4*10^{-6}\frac{J}{s}$ (1)

Furthermore you calculate the energy of a photon with a wavelength of 600nm, by using the following formula:

$E_p=h\frac{c}{\lambda}$ (2)

c: speed of light = 3*10^8 m/s

h: Planck's constant = 6.626*10^-34 Js

λ: wavelength = 600*10^-9 m

You replace the values of the parameters in the equation (2):

$E_p=(6.626*10^{-34}Js)\frac{3*10^8m/s}{600*10^{-9}m}=3.131*10^{-19}J$

Next, you calculate the quotient between the power of the light (equation (1)) and the energy of the photon:

$n=\frac{P}{E_p}=\frac{1.4*10^{-6}J/s}{3.131*10^{-19}J}=4.47*10^{12}photons$

The number of photons is 4.47*10^12

2) The kinetic energy of the electrons emitted by the metal is given by the following formula:

$K=E_p-\Phi$ (3)

Ep: energy of the photons

Φ: work function of the metal = 1.7 eV

You first convert the energy of the photons to eV:

$E_p=3.131*10^{-19}J*\frac{6.242*10^{18}eV}{1J}=1.954eV$

You replace in the equation (3):

$K=1.95eV-1.7eV=0.25eV$

The kinetic energy of the electrons emitted by the metal is 0.25 eV

6 0

4 years ago

A rider on a bike with the combined mass of 100 kg attains a terminal speed of 15 m/s on a 12% slope. Assuming that the only for

vlabodo [156]

Answer:

0·95

Explanation:

Given the combined mass of the rider and the bike = 100 kg

Percent slope = 12%

∴ Slope = 0·12

Terminal speed = 15 m/s

Frontal area = 0·9 m²

Let the slope angle be β

tanβ = 0·12

As it attains the terminal speed, the forces acting on the combined rider and the bike must be balanced and therefore the rider must be moving download as the directions of one of the component of weight and drag force will be in opposite directions

The other component of weight will get balance by the normal reaction and you can see the figure which is in the file attached

From the diagram m × g × sinβ = drag force

Drag force = 0·5 × d × $C_{D}$ × v² × A

where d is the density of the fluid through which it flows

$C_{D}$ is the drag coefficient

v is the speed of the object relative to the fluid

A is the cross sectional area

As tanβ = 0·12

∴ sinβ = 0·119

Let the fluid in this case be air and density of air d = 1·21 kg/m³

m × g × sinβ = 0·5 × d × $C_{D}$ × v² × A

100 × 9·8 ×0·119 = 0·5 × 1·21 × $C_{D}$ × 15² × 0·9

∴ $C_{D}$ ≈ 0·95

∴ Drag coefficient is approximately 0·95

4 0

3 years ago

Read 2 more answers

Pauline is going on a picnic and bringing some sandwiches. She wants to keep the sandwiches cold for as long as possible by putt

Alja [10]

Answer:

The correct answer is plastic.

Explanation:

To keep sandwiches cold as long as possible by putting them in a cooler the best material is plastic. The plastic is a thermal insulator used for different uses. One of them is to maintain the temperature in closed containers. Metal and aluminum allow the temperature to flow more easily and glass is not a suitable material for building the cooler.

Have a nice day!

5 0

3 years ago