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stiv31 [10]
3 years ago
9

To understand thermal linear expansion in solid materials. Most materials expand when their temperatures increase. Such thermal

expansion, which is explained by the increase in the average distance between the constituent molecules, plays an important role in engineering. In fact, as the temperature increases or decreases, the changes in the dimensions of various parts of bridges, machines, etc., may be significant enough to cause trouble if not taken into account. That is why power lines are always sagging and parts of metal bridges fit loosely together, allowing for some movement. It turns out that for relatively small changes in temperature, the linear dimensions change in direct proportion to the temperature.
For instance, if a rod has length L0 at a certain temperature T0 and length L at a higher temperature T, then the change in length of the rod is proportional to the change in temperature and to the initial length of the rod: L - L0 = αL0(T - T0),
or
ΔL = αL0ΔT.
Here, α is a constant called the coefficient of linear expansion; its value depends on the material. A large value of α means that the material expands substantially as the temperature increases; smaller values of α indicate that the material tends to retain its dimensions. For instance, quartz does not expand much; aluminum expands a lot. The value of α for aluminum is about 60 times that of quartz!
Questions:
A) Compared to its length in the spring, by what amount ΔLwinter does the length of the bridge decrease during the Teharian winter when the temperature hovers around -150°C?
B) Compared to its length in the spring, by what amount ΔLsummer does the length of the bridge increase during the Teharian summer when the temperature hovers around 700°C?

Physics
1 answer:
Marat540 [252]3 years ago
5 0

Answer:

Check the explanation

Explanation:

Kindly check the attached image below to see the step by step explanation to the question above.

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Can a goalkeeper at her/ his goal kick a soccer ball into the opponent’s goal without the ball touching the ground? The distance
PSYCHO15rus [73]

Answer:

No she cannot.

Explanation:

Let v_h be the horizontal component of the ball velocity when it's kicked, assume no air resistance, this is a constant. Also let v_v be the vertical component of the ball velocity, which is affected by gravity after it's kicked.

The time it takes to travel 95m accross the field is

t = 95 / v_h or v_h = 95/t

t is also the time it takes to travel up, and the fall down to the ground, which ultimately stops the motion. So the vertical displacement after time t is 0

s = v_vt + gt^2/2= 0

where g = -9.8m/s2 in the opposite direction with v_v

v_vt - 4.9t^2 = 0

v_vt = 4.9t^2

v_v = 4.9t

Since the total velocity that the goal keeper can give the ball is 30m/s

v = v_v^2 + v_h^2 = 30^2 = 900

(4.9t)^2 + \left(\frac{95}{t})^2 = 900

24.01t^2 + \frac{9025}{t^2} = 900

Let substitute x = t^2 > 0

24.01 x + \frac{9025}{x} = 900

We can multiply both sides by x

24.01 x^2 + 9025 = 900x

24.01x^2 - 900x + 9025 = 0

t= \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}

t= \frac{900\pm \sqrt{(-900)^2 - 4*(24.01)*(9025)}}{2*(24.01)}

As (-900)^2 - 4*24.01*9025 = -56761 < 0

The solution for this quadratic equation is indefinite

So it's not possible for the goal keeper to do this.

6 0
3 years ago
A bird flying 5.0 m overhead sees me drop it, and starts to dive straight down towards the bread the instant I release it. She c
gladu [14]

Answer:

15

Explanation:

muntiply the 5.0.3.0 ,you will get ans

5 0
3 years ago
A truck moves 60 km West, and then 80 km North, and then
stira [4]

▪▪▪▪▪▪▪▪▪▪▪▪▪  {\huge\mathfrak{Answer}}▪▪▪▪▪▪▪▪▪▪▪▪▪▪

Distance travelled by the truck is ~

  • \boxed{240 \:  \: km}

And it's displacement is ~

  • \boxed{0 \:  \: km}

\large \boxed{ \mathfrak{Step\:\: By\:\:Step\:\:Explanation}}

See the diagram in attachment for reference ~

Let O be the initial point, It travels 60 km towards west till point B and then 80 km towards north till point P and returns to initial point O in a straight line, now as we can observe here, it forms a right angled Triangle.

The measure of two legs is 60 km and 80 km, let's find the hypotenuse ~

According to Pythagoras theorem ~

hypotenuse² = sum of squares of other two legs

that is ~

  • h {}^{2}  = 60 {}^{2}  + 80 {}^{2}

  • {h}^{2}  = 3600 + 640 0

  • h {}^{2}  = 10000

  • h =  \sqrt{10000}

  • h =  \sqrt{100 \times 100}{}

  • h = 100 \:  \: km

So, the distance between the point A and O is 100 km

Now, The total distance is equal to the distance covered through actual path that is ~

  • 60 km + 80 km + 100 km

  • 240 km

And displacement is the distance between the final point and initial point, but since the truck returns to the point from where it started the journey, so the final and initial point is same therefore displacement is equal to 0.

4 0
3 years ago
Two sources of error and precaution in the centre of gravity experiment​
Karo-lina-s [1.5K]

Answer:

The answer to this question is given below in this explanation sections.

Explanation:

The weight of an object is concentrated at the center of gravity.The term center of gravity is used interchangeably with center of mass.For a symmetrical object the center of mass is located  at the geometric  center of the object.If the object is not symmetric we can determined the center of mass using the mentioned below.

Materials:

  • cardboard
  • weight(washer,bolt,or fishing weight)
  • hole punch
  • pencil

Procedure:

  1. Cut the cardboard into a strange shape.Do not use a circle,square,rectangle,or any other common geometric shape.
  2. Punch a hole near the edge of the cut-out cardboard piece and hang it from a nail.
  3. Place the weight, a washer or bolt, on a thread and tie it off.
  4. Hang the thread and weight from the nail in front of the cardboard.
  5. use a pencil to draw a plumb line down the cardboard where the thread touches.This mark your center  line from that hanging point.

conclusion:

             What would happen to the center of gravity of the shape if you were to spin it freely?

center of gravity experiment:

  1. Balance a ruler with a hammer.Take a rubber band or string and make a loose loop around the hammer and ruler. Make sure the end of the hammer is touching the ruler,and then positions the ruler at the edge of the table.
  2. Balance two forces with  a toothpick.A common magic  trick using the properties of center of gravity.The two forks are balanced on the edge of the glass by a toothpick.
  3. Stand with your back and feet against a wall.Have someone place quarter on the floor at your feet.Try to pick it cup.Most people cant make these adjustments.
  4. Stand against a wall sideways with your arm and leg touching the wall,with nothing to from the out away hold onto.Try to lift your other leg straight out away from the wall.you wont be able to do it.
  5. The girls away win chairs lifting challanges place dining chairs against a wall.Bend over the chair so that your head touches the wall and you upper body is parallel to the floor.lift the chair to your chest to your chest and then try to stand up.
7 0
3 years ago
An object with a mass of 2 kg has a force of 4 N acting on it. What is the acceleration of the object?
STatiana [176]
Answer: 2 m/s^2

Explain

£F=ma
net force = mass x acceleration
4N is a force acting on it
4N=(2kg) a
2kg is the mass
you divide the 2 over
and A= 2 m/s^2

8 0
3 years ago
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