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iogann1982 [59]
2 years ago
5

In the diagram, a force of 20 newtons is applied to a block. The block is in dynamic equilibrium. What is the magnitude and dire

ction of the frictional force?
A. 20 newtons in the direction of the applied force
B. 20 newtons opposite to the direction of the applied force
C. 20 newtons perpendicular to the direction of the applied force
D. 20 newtons in two directions, perpendicular and in the direction of the applied force
E. No friction is acting on the block.
Physics
2 answers:
ololo11 [35]2 years ago
8 0
The answer is B because it is true my teacher literally told me this last week! Good thing I remember
sladkih [1.3K]2 years ago
5 0

Answer:B 20 newtons opposite to the direction of the applied force

Explanation:

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Radioactive plutonium−239 (t1/2 = 2.44 × 105 yr) is used in nuclear reactors and atomic bombs. If there are 3.50 × 102 g of the
madam [21]

Answer:

t = 4.41 10⁻⁴ years

Explanation:

For this exercise we must use the concept of average life time, which is the time in which the quantity and substance decays in half

    T_{1/2}  = ln2 / λ

Let's calculate the decay constant of plutonium

    λ  = ln2 /  T_{1/2}

    λ  = ln 2 / 2.44 10⁵  

    λ  = 2.84 10⁻⁶  s⁻¹

Radioactive decay is a first order process

     N = No e (-λ   t)

Where N is the number of nuclei, the mass is this by molecular weight

    m = N PM

    m / PM = m₀ / PM e (- λ  t)

    m / m₀ = e (- λ  t)

    -λ  t = ln (m / m₀)

     t = -1 /λ   ln (m/m₀)

     t = - 1 / 2.84 10⁻⁶   ln (0.1 / 0.35)

     t = 4.41 10⁻⁴ years

7 0
3 years ago
In 2014, about how far in meters would you have to travel on the surface of the Earth from the North Magnetic Pole to the Geogra
pogonyaev

Answer:

267.07 km

Explanation:

We have given the radius of the earth = 6378.1 km

In 2014 the difference between the magnetic north pole and geographical north pole is 2.40°

2.40°=2.40\times \frac{\pi }{180}=0.041866 radian

We know that linear distance is given by S=R\Theta =6378.1\times 0.041866=267.07km

So we have to travel 267.07 km in going from magnetic north pole to geographic north pole

3 0
3 years ago
An ostrich can run at speeds of up to 72 kilometers per hour. How long will it take an ostrich to run 1.5 kilometers at this top
tatiyna
S=d/t
T=d/s
= 1.5/72
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6 0
3 years ago
Why does the speed of an object change when a force acts on it?
Crazy boy [7]
It changes because force is somewhat like pressure. Force is continuously against the object so as a result, speed changes .
7 0
3 years ago
A spherically spreading EM wave comes from an 1800-W source. At a distance of 5.0 m, what is the intensity, and what is the rms
babymother [125]

Answer:

The intensity of the EM wave is 5.729 W/m²

The rms value of the electric field is 46.452 V/m

Explanation:

Given;

power of the electromagnetic wave, P = 1800 W

The intensity of light is given by;

I = P / A

Where;

A is the surface area of the sphere = 4πr²

A is the surface area of the sphere = 4π(5)²

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The intensity is calculated as;

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I = (1800) / (314.2)

I = 5.729 W/m²

The rms value of the electric field is given by;

E_{rms} = \sqrt{\frac{I}{c \epsilon _o}}\\\\E_{rms} = \sqrt{\frac{5.729}{(3*10^8)( 8.85*10^{-12})}}\\\\E_{rms} = 46.452 \ V/m

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4 years ago
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