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meriva
3 years ago
10

Some thermal containers have layers of materials to keep drinks cold for as long as possible. Which design would help keep ice f

rozen for the longest period?​
A. Inner core of steel, no air gap, outer layer of plastic

B. Inner core of steel, air gap, outler layer of glass

C. Inner core of steel, no air gap, outer layer of plastic

D. Inner core of glass, air gap, outer layer of glass


I know A. and C. are the same, but those are my options.
Physics
2 answers:
MakcuM [25]3 years ago
8 0

Answer:

D.

Explanation:

grin007 [14]3 years ago
5 0
The answer is D correct me if I’m wrong
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The principles of magnetism apply everywhere on earth. What does this tell us about God and His character?
Bas_tet [7]

Answer:

God is omnipresent.

Explanation:

This means God is everywhere and He works where ever we are in the world

3 0
3 years ago
Traumatic brain injury such as a concussion results when the head undergoes a very large acceleration. Generally an acceleration
eimsori [14]

The complete text of the problem is:

<em>"Traumatic brain injury such as concussion results when the head undergoes a very large acceleration. Generally, an acceleration less than 800 m/s2 lasting for any length of time will not cause injury, whereas an acceleration greater than 1000 m/s2 lasting for at least 1 ms will cause injury. Suppose a small child rolls off a bed that is 0.43 m above the floor. If the floor is hardwood, the child's head is brought to rest in approximately 1.8 mm. If the floor is carpeted, this stopping distance is increased to about 1.1 cm. Calculate the magnitude and duration of the deceleration in both cases, to determine the risk of injury. Assume the child remains horizontal during the fall to the floor. Note that a more complicated fall could result in a head velocity greater or less than the speed you calculate. "</em>

<em />

<u>Solution:</u>

1) Acceleration: -2336 m/s^2 on the hardwood floor, -382 m/s^2 on the carpeted floor

First of all, we need to calculate the speed of the child just before he hits the floor. This can be done by using the equation

v^2 - u^2 = 2ad

where

v is the final speed

u = 0 is the initial speed (the child starts from rest)

a = g = 9.8 m/s^2 is the acceleration of gravity

d = 0.43 m is the distance covered by the child as he falls from the bed

Solving for v,

v=\sqrt{2ad}=\sqrt{2(9.8)(0.43)}=2.9 m/s

Now we can analyze the moment of the collision. The child hits the floor with an initial speed of v = 2.9 m/s, and he comes to a stop, so the final speed is v' = 0. If the floor is hardwood, the stopping distance is

d = 1.8 mm = 0.0018 m

So we can find the acceleration by using again the equation

v'^2 - v^2 = 2ad

Solving for a,

a=\frac{v'^2 - v^2}{2d}=\frac{0-2.9^2}{2(0.0018)}=-2336 m/s^2

For the carpeted floor instead,

d=1.1 cm = 0.011 m

therefore the acceleration is

a=\frac{v'^2 - v^2}{2d}=\frac{0-2.9^2}{2(0.011)}=-382 m/s^2

2) Duration: 1.24 ms for the hardwood floor, 7.59 ms for the carpeted floor

We can find the duration of the collision in both cases by using the equation of the acceleration

a=\frac{v'-v}{t}

where

v' = 0

v = 2.9 m/s

For the hardwood floor,

a=-2336 m/s^2

So the duration of the collision is

t = \frac{v'-v}{a}=\frac{0-2.9}{-2336}=0.00124 s = 1.24 ms

For the carpeted floor,

a=-382 m/s^2

So the duration of the collision is

t = \frac{v'-v}{a}=\frac{0-2.9}{-382}=0.00759 s = 7.59 ms

We can now comment the results using the initial statement of the problem:

"Generally an acceleration less than 800 m/s2 lasting for any length of time will not cause injury, whereas an acceleration greater than 1,000 m/s2 lasting for at least 1ms will cause injury"

Therefore, the fall on the hardwood floor can result in injury (since the acceleration is greater than 1,000 m/s2 for more than 1 ms), while the fall on the carpeted floor is not dangerous (much less than 1000 m/s^2).

8 0
3 years ago
A car traveling in a straight line has a velocity of 6m/s at some instant. After 6.32s its velocity is 13.2m/s . What is the ave
NeX [460]
Average acceleration  =  (change in speed) / (time for the change) .

Average acceleration  =  (13.2 - 6) / (6.32) = 7.2 / 6.32 = about  <em>1.139... m/s²</em> .
8 0
3 years ago
Arace car accelerates uniformly at 11.3 m/s2. If the race car starts from rest how fast will it
Ganezh [65]

Answer:

75.71 m/s

Explanation:

From equation of motion, acceleration is given by

a=\frac {v-u}{t}where v is the final velocity, u is the initial velocity and t is time taken.

Making v the subject of the above formula

v=at+u

Substituting 6.7 s for time, t and 11.3 for a and taking u as zero since it starts from rest

v=11.3*6.7=75.71 m/s

7 0
3 years ago
An object is accelerating from rest at a rate of 3 m/s2.How long will it take the object to attain 18 m/s ? *
Temka [501]
Initial velocity =0, a=3m/s2, final velocity =18m/s, 18=3t, t=6 sec
7 0
3 years ago
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