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k0ka [10]
4 years ago
9

A copper telephone wire has essentially no sag between poles 36.0 m apart on a winter day when the temperature is −20.0°C. How m

uch longer is the wire on a summer day when the temperature is 34.0°C?
Physics
1 answer:
RideAnS [48]4 years ago
4 0

Answer:

The extension is  \Delta  L  = 0.033 \ m

Explanation:

From the question we are told that  

     The length of the wire on a winter day is    L_w =  36.0 \ m

      The temperature on the winter day is  T_w  =  -20.0 ^o C

      The temperature on a summer day is  T_s  =  34.0 ^0 C

The the extension of the wire on a summer day is mathematically represented as

          \Delta  L  = \alpha L_w [T_s - T_w]

Where  

      \alpha is the  coefficient of linear expansion of copper with a values \alpha  =  17 *10^{-6}

substituting value  

      \Delta  L  = 17 *10^{-6} *  36.0  [34  - [-20]]

      \Delta  L  = 0.033 \ m

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RoseWind [281]
About 2000 years ago Chinese discovered it, couple hundred years later what happened was it was figured out our compasses are not completely accurate, because of magnetic rock can throw off the compasses it’s self it reads by push and pull but that was what was used to navigate back then.
4 0
3 years ago
A 24 kg child slides down a 3.3-m-high playground slide. She starts from rest, and her speed at the bottom is 3.0 m/s.a. What en
Gelneren [198K]

Answer:

(a) Potential energy of the child is converted into the kinetic energy at the bottom off the slide and a part of which is lost into friction generating heat between the contact surfaces.

(b) U=668.16\ J

Explanation:

Given:

  • mass of the child, m=24\ kg
  • height of the slide, h=3.3\ m
  • initial velocity of the child at the slide, v_i=0 m.s^{-1}
  • final velocity of the child at the bottom of slide, v_f=3\ m.s^{-1}

(a)

∴The initial potential energy of the child is converted into the kinetic energy at the bottom off the slide and a part of which is lost into friction generating heat between the contact surfaces.

Initial potential energy:

PE=m.g.h

PE=24\times 9.8\times 3.3

PE=776.16\ J

Kinetic energy at the bottom of the slide:

KE=\frac{1}{2} m.v^2

KE= 0.5\times 24\times 3^2

KE= 108\ J

(b)

Now, the difference in the potential and kinetic energy is the total change in the thermal energy of the slide and the seat of her pants.

This can be given as:

U=PE-KE

U=776.16-108

U=668.16\ J

4 0
3 years ago
You and your neighbour are shovelling snow. If your neighbour pushes a shovel four times as far as you do but exerts only a half
geniusboy [140]

Answer:

The neighbour

Double your work

Explanation:

Work is a product of force and distance, expressed as W=Fd where W is work in Nm, F is applied force and d is the distance in m

Since your neighbour pushes 4 times then you just push 1m when he pushes 4m, that is an example. Also, since the neighbour only exerts half the force ie 0.5N then you exert full force of 1N

Work from your neighbour will be 4d*0.5F=2dF

Work from you will be dF

Clearly, 2dF=2(dF) hence the neigjbour exerts double work

3 0
4 years ago
(based on 15-103 in the text) At an initial instant, a 4-lb ball B is traveling around in a circle of radius r1 = 3 ft with a sp
lisov135 [29]

Answer:

a

 v_r =8.65 \ ft/s

b

  W_{1-2} =  3.24 \  ft \cdot lb

Explanation:

From the question we are told that

  The mass of the ball is m  =  4 \  lb

  The radius is  r= 3 \  ft

   The speed is v_B_1  =  4.8 \ ft /s

    The speed of the attached cord is  v_c =2.2 \  ft

   The position that is been considered is  r_1 =  2 \  fth

Generally according to the law of angular momentum conservation

   L_a =  L_b

Here L_a is the initial  momentum of the ball which is mathematically represented as

      L_a  =  m*  v_B_1 *  r

while  

L_b is the  momentum of the ball  at  r =  2 ft which is mathematically represented as

       L_a  =  m*  v_B_2 *  r_1

So

      m*  v_B_1 *  r = m*  v_B_2 *  r_1

=>      4.8 *  3 =  v_B_2 *  2

=>     v_B_2 =  7.2 \  ft/s

Generally the resultant velocity of the ball is  

      v_r = \sqrt{v_B_2^2 + v_B_1^2   }

=>   v_r = \sqrt{7.2^2 + 4.8^2   }

=>   v_r =8.65 \ ft/s

Generally according to equation for principle of work and energy we have that

    K_1 + \sum W_{1-2} = K_2

Here K_1 is the initial kinetic energy of the ball which is mathematically represented as

K_1  =  \frac{1}{2}  *  m* v_B_1^2

While  \sum W_{1-2} is the sum of the total  workdone by the ball

and  K_2 is the final kinetic energy of the ball  which is mathematically represented as  K_2  =  \frac{1}{2}  *  m* v_r^2

So

     \sum W_{1-2} =  \frac{1}{2}  *  m  (v_r^2  -  v_B_1^2)

Here  m is the mass which is mathematically represented as

     m = \frac{W}{g} here W is the weight in  lb and  g is the acceleration due to gravity which is g =  32 \ ft/s^2

So

    \sum W_{1-2} =  \frac{1}{2}  *  \frac{4}{32} *   (8.65^2  -  4.8^2)

=>   W_{1-2} =  3.24 \  ft \cdot lb

   

   

3 0
3 years ago
Which of the following is the best hypothesis for this experiment? (Remember that the variable we are going to manipulate is the
Soloha48 [4]

answer would be A becuz that's the only reasonable choice according to real life situations

7 0
4 years ago
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