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Ostrovityanka [42]
3 years ago
14

The earliest method of food preservation was the icebox. a. True b. False

Physics
1 answer:
fredd [130]3 years ago
7 0
False, the ice box was invented in the 1930's, the earliest for of food preservation was probably a shaded place, cave or smoking the food. the earliest forms of food preservation are hard to prove and I don't know what they are either I was just making and educated guess. 
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The small spherical planet called "Glob" has a mass of 7.88×10^18 kg and a radius of 6.32×10^4 m. An astronaut on the surface of
Oksi-84 [34.3K]

Answer: The small spherical planet called "Glob" has a mass of 7.88×1018 kg and a radius of 6.32×104 m. An astronaut on the surface of Glob throws a rock straight up. The rock reaches a maximum height of 1.44×103 m, above the surface of the planet, before it falls back down.

1) the initial speed of the rock as it left the astronaut's hand is 19.46 m/s.

2) A 36.0 kg satellite is in a circular orbit with a radius of 1.45×105 m around the planet Glob. Then the speed of the satellite is 3.624km/s.

Explanation: To find the answer, we need to know about the different equations of planetary motion.

<h3>How to find the initial speed of the rock as it left the astronaut's hand?</h3>
  • We have the expression for the initial velocity as,

                           v=\sqrt{2gh}

  • Thus, to find v, we have to find the acceleration due to gravity of glob. For this, we have,

                       g_g=\frac{GM}{r^2} =\frac{6.67*10^{-11}*7.88*10^{18}}{(6.32*10^4)^2}= 0.132

  • Now, the velocity will become,

                        v=\sqrt{2*0.132*1.44*10^3} =19.46 m/s

<h3>How to find the speed of the satellite?</h3>
  • As we know that, by equating both centripetal force and the gravitational force, we get the equation of speed of a satellite as,

                       v=\sqrt{\frac{GM}{r} } =\sqrt{\frac{6.67*10^{-11}*7.88*10^{18}}{1.45*10^5} } =3.624km/s

Thus, we can conclude that,

1) the initial speed of the rock as it left the astronaut's hand is 19.46 m/s.

2) A 36.0 kg satellite is in a circular orbit with a radius of 1.45×105 m around the planet Glob. Then the speed of the satellite is 3.624km/s.

Learn more about the equations of planetary motion here:

brainly.com/question/28108487

#SPJ4

3 0
2 years ago
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A ray diagram without the produced image is shown.
Mashutka [201]
The answer is real and smaller than the object. The image point of the top of the object is the point where the two refracted rays intersect. Tracing the entire image having the same distance from the mirror as the image of the top of the object and with the bottom on the principal axis. Hence, a real inverted image will be formed for an object outside the focal point. 
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3 years ago
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Scientists classify rocks by
Mashcka [7]
Composition and texture
6 0
3 years ago
A 15g bullet is fired horizontally into a 3kg block of wood suspended by a long cord. Assume that the bullet remains in the bloc
Varvara68 [4.7K]

Answer:

261.3 m/s

Explanation:

Mass of bullet=m=15 g=\frac{15}{1000}=0.015 kg

1 kg=1000g

Mass of block=M=3 kg

d=0.086 m

Total mass =M+m=3+0.015=3.015 kg

K.E at the time strike=Gravitational potential energy at the end of swing

\frac{1}{2}(m+M)^2V^2=(m+M)gh

Using g=9.8m/s^2

Substitute the values

\frac{1}{2}(3.015)V^2=3.015\times 9.8\times 0.086

V^2=\frac{2\times 3.015\times 9.8\times 0.086}{3.015}

V=\sqrt{2\times 3.015\times 9.8\times 0.086}}

V=1.3m/s

Velocity after collision=V=1.3 m/s

Velocity of block=v'=0

Using conservation law of momentum

mv+Mv'=(m+M)V

Using the formula

0.015v+3(0)=3.015(1.3)

0.015v=3.015(1.3)

v^2=\frac{3.015(1.3)}{0.015}=261.3

v=261.3 m/s

5 0
3 years ago
un motor electric efectueaza un lucru mecanic de 864 j in 0.5 min.tensiunea la bornele sale este de 12v si este parcurs de un cu
GrogVix [38]

Answer:

96%

Explanation:

To find the values of the motor efficiency you use the following formula:

E=\frac{P_o}{P_i}100

P_o: output power = 864J/0.5min=864J/30s=28.8W

P_i: input power = I*V = (3A)(12V) = 36W

By replacing this values you obtain:

E=\frac{28.8W}{30W}*100=96\%

hence, the motor efficiency is about 96%

traslation:

Pentru a găsi valorile eficienței motorului, utilizați următoarea formulă:

P_o: putere de ieșire = 864J / 0.5min = 864J / 30s = 28.8W

P_i: putere de intrare = I * V = (3A) (12V) = 36W

Înlocuind aceste valori obțineți:

prin urmare, eficiența motorului este de aproximativ 96%

3 0
3 years ago
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