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Anna007 [38]
3 years ago
5

In the lab you place a beaker that is half full of water (density pw ) on a scale. You now use a light string to suspend a piece

of metal of volume V in the water. The metal is completely submerged, and none of the water spills out of the beaker.
Give a symbolic expression for the change in reading of the scale.Express your answer in terms of the variables pw, V, and appropriate constants.N2-N1=___________
Physics
1 answer:
Radda [10]3 years ago
6 0

Answer:

N2- N1 = \rho_{w}  V g

Explanation:

Let's use for this exercised the equilibrium relationship

        ∑ F = 0

        N -W = 0

        N = W = mg

Let's use density redefinition

       ρ = m / v

       m = ρ V

       N₁ = (ρ V) g

Repeat for when the liquid is submerged, in this case an upward thrust appears as a result of the water dispensed (rgow)

        N₂ + B - W = 0

        N₂ = W - B

        B = m_{water} g

        \rho_{w} = m / V

         m_{w}  =  \rho_{w}  V

        N = ρ V g -  \rho_{w}  Vg

        N2 = N1 +   \rho_{w}  V g

        N2- N1 = \rho_{w}  V g

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A steady current I flows through a wire of radius a. The current density in the wire varies with r as J = kr, where k is a const
grin007 [14]

Answer:

Explanation:

we can consider an element of radius r < a and thickness dr.  and Area of this element is

dA=2\pi r dr

since current density is given

J=kr

then , current through this element will be,

di_{thru}=JdA=(kr)(2\pi\,r\,dr)=2\pi\,kr^2\,dr

integrating on both sides between the appropriate limits,

\int_0^Idi_{thru}=\int_0^a2\pi\,kr^2\,dr&#10;\\\\&#10;I=\frac{2\pi\,ka^3}{3} -------------------------------(1)

Magnetic field can be found by using Ampere's law

\oint{\vec{B}\cdot\,d\vec{l}}=\mu_0\,i_{enc}

for points inside the wire ( r<a)

now, consider a point at a distance 'r' from the center of wire. The appropriate Amperian loop is a circle of radius r.

by applying the Ampere's law, we can write

\oint{\vec{B}_{in}\cdot\,d\vec{l}}=\mu_0\,i_{enc}&#10;

by symmetry \vec{B} will be of uniform magnitude on this loop and it's direction will be tangential to the loop.

Hence,

B_{in}\times2\pi\,l=\mu_0\int_0^r(kr)(2\pi\,r\,dr)=&#10;\\\\2\pi\,B_{in} l=2\pi\mu_0k \frac{r^3}{3}&#10;\\\\B_{in}=\frac{\mu_0kl^2}{3}&#10;

now using equation 1, putting the value of k,

B_{in} = \frac{\mu_{0} l^2 }{3 } \,\,\, \frac{3I}{2 \pi a^3}&#10;\\\\B_{in} = \frac{ \mu_{0} I l^2}{2 \pi a^3}&#10;

B)

now, for points outside the wire ( r>a)

consider a point at a distance 'r' from the center of wire. The appropriate Amperian loop is a circle of radius l.

applying the Ampere's law

\oint{\vec{B}_{out}\cdot\,d\vec{l}}=\mu_0\,i_{enc}&#10;

by symmetry \vec{B} will be of uniform magnitude on this loop and it's direction will be tangential to the loop. Hence

B_{out}\times2\pi\,r=\mu_0\int_0^a(kr)(2\pi\,r\,dr)&#10;\\\\2\pi\,B_{out}r=2\pi\mu_0k\frac{a^3}{3}&#10;\\\\B_{out}=\frac{\mu_0ka^3}{3r}&#10;

again using,equaiton 1,

B_{out}= \mu_0 \frac{a^3}{3r} \times \frac{3 I}{2 \pi a^3}&#10;\\\\B_{out} = \frac{ \mu_{0} I}{2 \pi r}

8 0
3 years ago
Which of these statements are true about hydroelectric power? Check all that are true. It is the most widely used renewable ener
IRINA_888 [86]

Answer:

the last one is triu!!!!!!

7 0
3 years ago
Fill in the blanks below:<br><br> Urgently need help!!!
miskamm [114]

Answer:

In a circuit ,<u> VOLTAGE </u>can be said to be the "source" or the "push of electrons". This push then creates what is known as a <u> CURRENT , </u>which is the flow of electric charge through the circuit. This flow can the slowed down or restricted by <u>RESISTOR </u>, and this is also what can be harnessed in order to use electric <u>ENERGY </u>.

Explanation:

Voltage:

It is the 'push' that causes charges to move in a wire or other electrical conductor, also it is a Source input to the electric circuit.

Measured in Volts.

Current:

An electric current is the rate of flow of electric charge from a point or through a region.

Measured in Ampere.

Resistor:

Resistor is used to resist the flow of charge or to resist the current called as Resistance.

Measured in Ohms.

Electric Energy:

Electrical energy is a form of energy resulting from the flow of electric charge.

Measured in Joules.

In a circuit , voltage can be said to be the "source" or the "push of electrons". This push then creates what is known as a current, which is the flow of electric charge through the circuit. This flow can the slowed down or restricted by resistor, and this is also what can be harnessed in order to use electric energy.

8 0
3 years ago
The total electric flux from a cubical box 26.0 cm on a side is 1840 N m2/C. What charge is enclosed by the box?
vitfil [10]

The expression of the electric flux is

\Phi = \frac{Q}{\epsilon_0}

Here,

Q = Total charge enclosed in the closed surface

\epsilon_0 = Permittivity due to free space

Rearranging to find the charge,

Q = \epsilon_0 \Phi

Replacing with our values we have finally

Q = (8.85*10^{-12}F\cdot m^{-1})(1.84*10^3 N\cdot m^2/C)

Q = 1.6284*10^{-8} C (\frac{10^9nC}{1C})

Q = 0.1684nC

The charge enclosed by the box is 0.1684nC

The sign of the charge can be decided by using the direction of the flux. The charge enclosed by the cube can be calculated by using the electric flux and the permitivity of free space.

7 0
3 years ago
If it takes 50.0 seconds to lift 10.0 Newtons of books to a height of 7.0
Ilya [14]
Work of the force = 10 N

Time required for the work = 50 sec

Height = 7 m

We are given with the value of work and time in the question.

Substitute the values in the formula of power and then you'll get the power required.

We know that,

w = Work

p = Power

t = Time

By the formula,

Given that,
Work (w) = 7 m = 70 Joules
Time (t) = 50 sec
Substituting their values,

p = 70/50

p = 1.4 watts

Therefore, the power required is 1.4 watts.

Hope it helps!
3 0
3 years ago
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