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ahrayia [7]
2 years ago
11

A large spool in an electrician's workshop has 70 m of insulation-coated wire coiled around it. When the electrician connects a

battery to the ends of the spooled wire, the resulting current is 2.7 A. Some weeks later, after cutting off various lengths of wire for use in repairs, the electrician finds that the spooled wire carries a 3.5-A current when the same battery is connected to it. What is the length of wire remaining on the spool
Physics
1 answer:
kramer2 years ago
7 0

Answer:

54.0m

Explanation:

#First we solve for

R=p(L/A)\\\\L=RA/p

let's denote the initial and final length of the rope as L_o, L_f respectively and given as:

L_o=\frac{R_oA}{p}, \ \ \ \ L_f=\frac{R_fA}{p}\ \  \ \ \ .....eqtn1\\

R_o is the initial resistance and Rf the final of the wire.

\frac{L_f}{L_o}=\frac{R_fA/P}{R_oA/P}=R_f/R_o\\\\\\or \ L_f=(R_f/R_o)L_o\ \ \ \ \ \ ...eqtn2

From R=V/I, the initial resistance R_o, \ and\  R_f of the spooled wire are:

R_o=V/I_o,\ \ \ \ \ \ R_f=V/I_f \ \ \ \ \ \  \....eqtn3\\

#Substituting eqtn 3 in 2, we get

L_f=(V/I_f)/(V/I_o)L_o\\\\=\frac{2.7A}{3.5A}\times 70m\\\\=54m

#the length of wire remaining on the spool is 54.0m

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A meter stick balances at the 50.0-cm mark. If a mass of 50.0 g is placed at the 90.0-cm mark, the stick balances at the 61.3-cm
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Answer:

126.99115 g

Explanation:

50 g at 90 cm

Stick balances at 61.3 cm

x = Distance of the third 0.6 kg mass

Meter stick hanging at 50 cm

Torque about the support point is given by (torque is conserved)

mgl_1=Mgl_2\\\Rightarrow M=\dfrac{ml_1}{l_2}\\\Rightarrow M=\dfrac{50\times (61.3-90)}{50-61.3}\\\Rightarrow M=126.99115\ g

The mass of the meter stick is 126.99115 g

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A brick of mass 5 kg is released from rest at a height of 3 m. How fast is it going when it hits the ground? Acceleration due to
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Taking into account the definition of kinetic, potencial and mechanical energy, when the brick hits the ground, it has a speed of 7,668 m/s.

<h3>Kinetic energy</h3>

Kinetic energy is a form of energy. It is defined as the energy associated with bodies that are in motion and this energy depends on the mass and speed of the body.

Kinetic energy is defined as the amount of work necessary to accelerate a body of a given mass and at rest, until it reaches a given speed. Once this point is reached, the amount of accumulated kinetic energy will remain the same unless there is a change in speed or the body returns to its state of rest by applying a force.

The kinetic energy is represented by the following expression:

Ec= ½ mv²

Where:

  • Ec is the kinetic energy, which is measured in Joules (J).
  • m is the mass measured in kilograms (kg).
  • v is the speed measured in meters over seconds (m/s).

<h3>Potential energy</h3>

On the other hand, potential energy is the energy that measures the ability of a system to perform work based on its position. In other words, this is the energy that a body has at a certain height above the ground.

Gravitational potential energy is the energy associated with the gravitational force. This will depend on the relative height of an object to some reference point, the mass, and the force of gravity.

So for an object with mass m, at height h, the expression applied to the gravitational energy of the object is:

Ep= m×g×h

Where:

  • Ep is the potential energy in joules (J).
  • m is the mass in kilograms (kg).
  • h is the height in meters (m).
  • g is the acceleration of fall in m/s².
<h3>Mechanical energy</h3>

Finally, mechanical energy is that which a body or a system obtains as a result of the speed of its movement or its specific position, and which is capable of producing mechanical work. Then:

Potential energy + kinetic energy = total mechanical energy

<h3>Principle of conservation of mechanical energy </h3>

The principle of conservation of mechanical energy indicates that the mechanical energy of a body remains constant when all the forces acting on it are conservative (a force is conservative when the work it does on a body depends only on the initial and final points and not the path taken to get from one to the other.)

Therefore, if the potential energy decreases, the kinetic energy will increase. In the same way, if the kinetics decreases, the potential energy will increase.

<h3>This case</h3>

A brick of mass 5 kg is released from rest at a height of 3 m. Then, at this height, the brick of mass has no speed, so the kinetic energy has a value of zero because it depends on the speed or moving bodies. But the potential energy is calculated as:

Ep= 5 kg× 9.8 \frac{m}{s^{2} }× 3 m

Solving:

<u><em>Ep= 147 J</em></u>

So, the mechanical energy is calculated as:

Potential energy + kinetic energy = total mechanical energy

147 J +  0 J= total mechanical energy

147 J= total mechanical energy

The principle of conservation of mechanical energy  can be applied in this case. Then, when the brick hits the ground, the mechanical energy is 147 J. In this case, considering that the height is 0 m, the potential energy is zero because this energy depends on the relative height of the object. But the object has speed, so it will have kinetic energy. Then:

Potential energy + kinetic energy = total mechanical energy

0 J +  kinetic energy= 147 J

kinetic energy= 147 J

Considering the definition of kinetic energy:

½  5 kg×v²= 147 J

v=\sqrt{\frac{2x147 J}{5 kg} }

v=7.668 m/s

Finally, when the brick hits the ground, it has a speed of 7,668 m/s.

Learn more about mechanical energy:

brainly.com/question/17809741

brainly.com/question/14567080

brainly.com/question/12784057

brainly.com/question/10188030

brainly.com/question/11962904

#SPJ1

6 0
1 year ago
A 5 newton force and a 7 newton force act concurrently on a point. As the angle between the forces is increased from 0 to 180 th
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Answer:

The magnitude of the resultant decreases from A+B to A-B

Explanation:

The magnitude of the resultant of two vectors is given by

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where

A is the magnitude of the first vector

B is the magnitude of the second vector

\theta is the angle between the directions of the two vectors

In the formula, A and B are constant, so the behaviour depends only on the function cos \theta. The value of cos \theta are:

- 1 (maximum) when the angle is 0, so the magnitude of the resultant in this case is

R=\sqrt{A^2 +B^2+2AB}=\sqrt{(A+B)^2}=A+B

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R=\sqrt{A^2 +B^2+0}=\sqrt{A^2+B^2}

- then it becomes negative, and continues to decrease, until it reaches a value of -1 when the angle is 180 degrees, and the magnitude of the resultant is

R=\sqrt{A^2 +B^2-2AB}=\sqrt{(A-B)^2}=A-B


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3 years ago
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