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egoroff_w [7]
2 years ago
15

The private papers of what scientist had to be decontaminated for two years in the 1990's before being put on file at the Nation

al Library in Paris? 577 points
Physics
1 answer:
SashulF [63]2 years ago
3 0
The answer is Marie Skłodowska Curie (AKA Marie Curie). She <span>lived her life awash in ionizing radiation. She would be carrying bottles of the radium and polonium in the pocket of her coat and put them in her desk drawer. 
So even after a century, her papers are still radioactive. Since the</span><span> most general isotope of radium, which is radium-226, has a half life of 1,601 years.</span>
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Suppose you lift a 20 kg box by a height of 1.0 m.
9966 [12]
W=mgh W=(20)(9.8)(1) w=196J
6 0
2 years ago
Read 2 more answers
What do astronomers use in addition to parallax to find the actual distance of stars that are close to Earth?
IgorLugansk [536]

Answer:

trigonometry (guessing)

Explanation:

ellipse: is the shape of an orbit : looks like an oval

periapsis : shortest distance between something like the moon and the planet its orbiting around like the earth

parallax is triangulation. like how gps works. looking at a star one day and then looking at it again 6 months later, an astronomer can see a difference in the viewing angle for the star. With trigonometry, the different angles yield a distance. This technique works for stars within about 400 light years of earth

https://science.howstuffworks.com/question224.htm

By comparing the intrinsic brightness to the star's apparent brightness we can calculate the distance of stars

1/r^2 rule states that the apparent brightness of a light source is proportional to the square of its distance.Jan 11, 2022

https://www.space.com/30417-parallax.html

alternative distance measurement for stars used by most astronomers is the parsec. A star with a parallax angle of 1 arcsecond has a distance of 1 parsec, or 1 parsec per arcsecond of parallax, which is about 3.26 light years

blossoms.mit.edu

.

7 0
2 years ago
1. Determine the image distance in each of the following.
miskamm [114]

It is given that for the convex lens,

Case 1.

u=−40cm

f=+15cm

Using lens formula

v

1

−

u

1

=

f

1

v

1

−

40

1

=

15

1

v

1

=

15

1

−

40

1

v=+24.3cm

The image in formed in this case at a distance of 24.3cm in left of lens.

Case 2.

A point source is placed in between the lens and the mirror at a distance of 40 cm from the lens i.e. the source is placed at the focus of mirror, then the rays after reflection becomes parallel for the lens such that

u=∞

f=15cm

Now, using mirror’s formula

v

1

+

u

1

=

f

1

v

1

+

∞

1

=

15

1

v=+15cm

The image is formed at a distance of 15cm in left of mirror

6 0
3 years ago
On which surface will the ball move the least distance?
Lisa [10]

Answer:

C) Frosted glass sheet

Explanation:

C) Frosted glass sheet

because it is Icy and slippery which make the ball move from its least distance

I hope you understand what it means

3 0
3 years ago
To Mr. H's disgust, a 450-g black crow is raiding the recently-filled bird feeder. As Mr. H runs out the back door with his broo
bagirrra123 [75]

Answer:

Actually it's 2.50 m/s, sorry

Explanation:

It is solved by using momentum conservation equation

combined mass of crow and feeder = 450+670=1120 gm

let the recoil speed of feeder be v m/s

Then applying momentum conservation we get;

1120×1.5 = 670×v

v= 2.50 m/s

the speed at which the feeder initially recoils backwards = 2.50 m/s

5 0
3 years ago
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