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2 years ago

!!!!100 POINTS!!!!

1 answer:

6 0

The event that had the greatest impact in astronomical history during this time period was the launch of Apollo 16.

The research of astronomy during the time period of 1970 - 1990 are given below as;

Date Event

1. 15 June 1974 Black Brant VC sounding rocket from White Sands.

2. 14 May 1973 Launch of Skylab, the USA's first space station

3. 26 July 1971 Launch of Apollo 15

<h3>What is Astronomy?</h3>

Astronomy is a branch of science that deals with celestial bodies and their relationship with each other.

From the information given about astronomy, between the time period 1970 - 1990 as it was on the 26th of December, 1974 that the Soviet space station Salyut-4 was launched.

The event that had the greatest impact in astronomical history during this time period was the launch of Apollo 16.

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A woman can row a boat at 4.0 mph is still water.

vovikov84 [41]

Answer:

1) $\theta=120^{\circ}$ from the positive x-axis.

2) $t=20\ min$

Explanation:

Given:

speed of rowing in still water, $v=4\ mph$

speed of water stream, $v_s=2\ mph$

we know that the direction of resultant of the two vectors is given by:

$tan\ \beta=\frac{v.sin\ \theta}{v_s+v.cos\ \theta}$

where:

$\beta=$ the angle of resultant vector from the positive x-axis.

$\theta =$ angle between the given vectors

When the rower wants to reach at the opposite end then:

$\beta =90^{\circ}$

so,

$tan\ 90^{\circ}=\frac{v.sin\ \theta}{v_s+v.cos\ \theta}$

$\Rightarrow v_s+v.cos\ \theta=0$

$2+4\times cos\ \theta=0$

$cos\ \theta=-\frac{1}{2}$

$\theta=120^{\circ}$ from the positive x-axis.

Now the resultant velocity of rowing in the stream:

$v_r=\sqrt{v^2+v_s^2+2\times v.v_s.cos\ \theta}$

$v_r=\sqrt{4^2+2^2+2\times 4\times 2\times cos\ 120}$

$v_r=12\ mph$

Therefore time taken to cross a 4 miles wide river:

$t=\frac{4}{12}$

$t=\frac{1}{3}\ hr$

$t=20\ min$

8 0

3 years ago

Two loudspeakers emit sound waves along the x-axis. The sound has maximum intensity when the speakers are 19 cm apart. The sound

Vanyuwa [196]

Answer:

Explanation:

The former is the case of constructive interference and the later case relates to destructive interference.

For listener, path difference is the separation of loudspeaker as listener is not standing in between the speaker.

If λ be the wave length

For constructive interference

19 = n λ

For destructive interference

29 = (2n+1) λ / 2

= n λ + λ / 2

= 19 + λ / 2

10 = λ / 2

λ = 20 cm

= 0. 20 m

7 0

3 years ago

In a radio, amplitude refers to encoding a wave with information by:

Ksivusya [100]

In radio communication, "amplitude modulation" refers to encoding a wave with information by adjusting the height (amplitude) of the waves. <em>(a)</em>

7 0

3 years ago

Read 2 more answers

The presence of foreign pottery in a well-dated Egyptian context shows that this type of pottery cannot be more recent than thos

Nutka1998 [239]

Answer:

TERMINUS ANTE QUEM

Explanation: Terminus ante quem is an Archeological an a Latin term used to describe the date before which an event or events took place,it is also used to show the date before which Archeological works have been deposited in a given area.

Example, a pottery dating to the 4th century AD found on a surface would give that pottery with a terminus ante quem of the 4thcentury AD.

This type of cross dating can either be TERMINUS ANTE QUEM OR TERMINUS POST QUEM.

3 0

3 years ago

A 2.44 kg block is pushed 1.55 m up a vertical wall with constant speed by a constant force of magnitude F applied at an angle o

svlad2 [7]

Answer:

The work done is L= 49.83 Joules

Explanation:

m= 2.44kg

d= 1.55m

α= 69.6°

g= 9.8 m/s²

μ= 0.691

F= ?

Fy= F*sin(α)

Fx= F*cos(α)

Fr= μ * Fx

Fr= μ * F*cos(α)

W= m*g

W= 23.91 N

Fy - W - Fr = 0

F*sin(α) - W - μ * F*cos(α) = 0

F* ( sin(α) - μ *cos(α) ) = W

F= W / ( sin(α) - μ *cos(α) )

F= 34.3 N

L= Fy * d

L= 49.83 J

6 0

4 years ago