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kogti [31]
3 years ago
7

A pesticide was applied to a population of roaches, and it was determined that the LD50 was 55mgkg. If the average mass of a roa

ch was 0.02kg, which of the following approaches will determine the dose in mg per roach?
Physics
1 answer:
zhannawk [14.2K]3 years ago
0 0

Answer:

55mg/kg * 0.02kg which gives 1.1 mg pesticides

Explanation:

(Options are missing)

If the average mass or weight of a roach is 0.02kg

And 55mg is needed per 1 kg roaches

The amount or size of pesticide required for 0.02kg roach is 55mg/kg * 0.02kg

Size = 55mg/kg * 0.02 kg

Size = 1.1mgkg/kg

Size = 1.1 mg

So, the size of pesticide required is 1.1mg

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Suppose that the acceleration of a model rocket is proportional to the difference between 160 ft/sec and the rocket's velocity.
Levart [38]

Answer:

Explanation:

Given ,

dv / dt = k ( 160 - v )

dv / ( 160 - v ) = kdt

ln ( 160 - v ) = kt + c , where c is a constant

when t = 0 , v = 0

Putting the values , we have

c = ln 160

ln ( 160 - v ) = kt + ln 160

ln ( 160 - v / 160 ) = kt

(160 - v ) / 160 = e^{kt}

1 - v / 160 = e^{kt }

v / 160 = 1 - e^{kt }

v = 160 ( 1 - e^{kt } )

differentiating ,

dv / dt = - 160k e^{kt }

acceleration a   = - 160k e^{kt }

given when t = 0 , a = 280

280 = - 160 k

k = - 175

a = - 160 x - 175 e^{kt}

a = 28000 e^{kt}

when a = 128  t = ?

128 = 28000 e^{kt}

e^{kt } = .00457

5 0
3 years ago
At what distance from a 27 mw point source of electromagnetic waves is the electric field amplitude 0. 060 v/m ?
n200080 [17]

The distance from a 27 mw point source of electromagnetic waves where the electric field amplitude 0. 060 v/m will be 21.21 m .

Electromagnetic waves or EM waves are waves that are created as a result of vibrations between an electric field and a magnetic field. In other words, EM waves are composed of oscillating magnetic and electric fields.

The highest point of a wave is known as 'crest' , whereas the lowest point is known as 'trough'. Electromagnetic waves can be split into a range of frequencies. This is known as the electromagnetic spectrum.

c = 3 * 10^{8} m/s

∈ = 8.85 * 10^{- 12} C^{2} / N/ m^{2}

E = 0. 060 v/m

I = P / 4πr^{2}

Also , I = c ∈ E^{2} /2

r^{2} = P / 4π I                                 equation 1

substituting the value of I in equation 1

r^{2} = 2 P / 4π (c ∈ E^{2} )

r^{2} = 2 * 27 * 10^{-3} / 4 * 3.14 * 3 * 10^{8} * 8.85 * 10^{- 12}  * (0.06)^{2}

r = 21.21 m

To learn more about Electromagnetic waves  here

brainly.com/question/12392559

#SPJ4

5 0
2 years ago
A disc of mass m slides with negligible friction along a flat surface with a velocity v. The disc strikes a wall head-on and bou
qwelly [4]

Answer:

-v/2

Explanation:

Given that:

  • a disc of mass m
  • Collides with the wall going through a sliding motion on on the plane smooth surface.
  • Upon rebounding from the wall its kinetic energy becomes one-fourth of the initial kinetic energy before collision.

<u>We know, kinetic energy is given as:</u>

KE_i=\frac{1}{2}. m.v^2

consider this to be the initial kinetic energy of the body.

<u>Now after collision:</u>

KE_f=\frac{1}{4}\times KE_i

KE_f=\frac{1}{4} \times \frac{1}{2}\times m.v^2

Considering that the mass of the body remains constant before and after collision.

KE_f=\frac{1}{2}\times m.(\frac{v}{2})^2

Therefore the velocity of the body after collision will become half of the initial velocity but its direction is also reversed which can be denoted by a negative sign.

3 0
3 years ago
How much heat must be removed from 200 pounds of blanched vegetables at 189 degrees F to freeze them to a temperature of 22 degr
Virty [35]

To solve this problem it is necessary to apply the concepts related to heat exchange in the vegetable and water.

By definition the exchange of heat is given by

Q =mc\Delta T

where,

m = mass

c = specific heat

\Delta T = Change in temperature

Therefore the total heat exchange is given as

\Delta Q = Q_w+Q_v

\Delta Q = m_wc_w(T_i-T_f)+m_vc_v(T_i-T_f)

Our values are given as,

Total mass is M_T = 200lb ,however the mass of solid vegetable and water is given as,

m_v= 0.4*200lb = 80lb

m_w=0.6*200lb=120lb

T_i = 183\°F\\T_f = 22\°F\\c_w = 1Btu/lbF\\c_v = 0.24Btu/lbF

Replacing at our equation we have,

\Delta Q = m_wc_w(T_i-T_f)+m_vc_v(T_i-T_f)

\Delta Q = (120)(1)(183-22)+(80)(0.24)(183-22)

\Delta Q = 22411.2Btu

Therefore the heat removed is 22411.2 Btu

6 0
3 years ago
How do air quality scientists ensure the air is cleaned? What steps do they take?
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Air sample of places around the world compared to clean air
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