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3 years ago

When did abundant fossil evidence first appear in geologic record?

Physics

2 answers:

GarryVolchara [31]3 years ago

5 0

About 540 million years ago.

mixer [17]3 years ago

3 0

I think 540 million yrs ago

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Two polarizers are oriented at 68 ∘ to one another. unpolarized light falls on them. part a what fraction of the light intensity

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Several motorboats with the same mass are used in an experiment. The forces of the different motors versus their accelerations a

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4 years ago

What is the frequency of a wave having a period equal to 18 seconds <br>

Ivanshal [37]

Explanation:

The time taken by a wave crest to travel a distance equal to the length of wave is known as wave period.

The relation between wave period and frequency is as follows.

T = \frac{1}{f}T=

where, T = time period

f = frequency

It is given that wave period is 18 seconds. Therefore, calculate the wave period as follows.

T = \frac{1}{f}T=

or, f = \frac{1}{T}f=

= \frac{1}{18 sec}

18sec

= 0.055 per second (1cycle per second = 1 Hertz)

or, f = 5.5 \times 10^{-2} hertz5.5×10 −2 hertz

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3 years ago

A circular loop of flexible iron wire has an initial circumference of 165.0 cm, but its circumference is decreasing at a constan

Fantom [35]

Answer:

(a). The emf induced in the loop is 0.005467 V.

(b). The direction of the current is clock wise direction.

Explanation:

Given that,

Circumference = 165.0 cm

Constant rate = 12.0 cm/s

Magnetic field = 0.500 T

Time = 9.0 s

We need to calculate the emf induced

Using formula of emf

$\epsilon=-\dfrac{d\phi}{dt}$

$\epsilon=-\dfrac{d(BA\cos\theta)}{dt}$

$\epsilon=B\dfrac{dA}{dt}$ ...(I)

Area of the coil is

$\dfrac{dA}{dt}=2\pi r\dfrac{dr}{dt}$

Put the value of area in equation (I)

$\epsilon=B\times2\pi r\dfrac{dr}{dt}$ ...(II)

The circumference of the coil is

$C=2\pi r$

$r = \dfrac{C}{2\pi}$

Put the value into the formula

$r=\dfrac{165.0}{2\pi}$

$r=26.26\ cm$

The rate of change of radius is

$\dfrac{dr}{dt}=\dfrac{12}{2\pi}$

$\dfrac{dr}{dt}=1.90\ cm/s$

The radius of the coil in 9 sec

$r=26.26-1.90\times9$

$r=9.16\ cm$

Put the value in the equation (I)

$\epsilon=-0.500\times2\pi\times9.16\times10^{-2}\times1.90\times10^{-2}$

$\epsilon=-0.005467\ V$

The magnitude of the emf

$|\epsilon|=0.005467\ V$

(b). Right hand rule :

According to right hand rule,

The thumb shows the direction of force, the index finger shows the direction of magnetic field and the middle finger shows the direction of current.

So, The direction of the current is clock wise direction.

Hence, (a). The emf induced in the loop is 0.005467 V.

(b). The direction of the current is clock wise direction.

8 0

4 years ago