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Arlecino [84]
3 years ago
8

A resistor with resistance R is connected to a battery that has emf 13.0 V and internal resistance r = 0.350 Ω . For what two va

lues of R will the power dissipated in the resistor be 81.0 W ?
Physics
1 answer:
makvit [3.9K]3 years ago
8 0

Answer:

R = 1,746 Ω

Explanation:

The power dissipated in the circuit is

   P = V I = V² / R

Let's find the current

   R = V² / P

Let's calculate

  R = 13²/81

   R = 2,096 Ω

This is total resistance

  R_total = R + r

   R = R_total - r

   R = 2,096 -0,350

   R = 1,746 Ω

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What is the pressure drop due to the Bernoulli Effect as water goes into a 3.00-cm-diameter nozzle from a 9.00-cm-diameter fire
Marianna [84]

Answer:

The pressure and maximum height are 1.58\times10^{6}\ N/m^2 and 161.22 m respectively.

Explanation:

Given that,

Diameter = 3.00 cm

Exit diameter = 9.00 cm

Flow = 40.0 L/s²

We need to calculate the pressure

Using Bernoulli effect

P_{1}+\dfrac{1}{2}\rho v_{1}^2+\rho g h_{1}=P_{2}+\dfrac{1}{2}\rho v_{2}^2+\rho g h_{2}

When two point are at same height so ,

P_{1}+\dfrac{1}{2}\rho v_{1}^2=P_{2}+\dfrac{1}{2}\rho v_{2}^2....(I)

Firstly we need to calculate the velocity

Using continuity equation

For input velocity,

Q=A_{1}v_{1}

v_{1}=\dfrac{Q}{A_{1}}

v_{1}=\dfrac{40.0\times10^{-3}}{\pi\times(1.5\times10^{-2})^2}

v_{1}=56.58\ m/s

For output velocity,

v_{2}=\dfrac{40.0\times10^{-3}}{\pi\times(4.5\times10^{-2})^2}

v_{2}=6.28\ m/s

Put the value into the formula

P_{1}-P_{2}=\dfrac{1}{2}\rho(v_{1}^2-v_{2}^2)

\Delta P=\dfrac{1}{2}\times1000\times(56.58^2-6.28^2)

\Delta P=1.58\times10^{6}\ N/m^2

(b). We need to calculate the maximum height

Using formula of height

\Delta P=\rho g h

Put the value into the formula

1.58\times10^{6}=1000\times9.8\times h

h=\dfrac{1.58\times10^{6}}{1000\times9.8}

h=161.22\ m

Hence, The pressure and maximum height are 1.58\times10^{6}\ N/m^2 and 161.22 m respectively.

8 0
3 years ago
A ball is kicked from the ground into the air at a velocity of 3 m/s at an angle 35° above the horizontal and hits the ground so
Dennis_Churaev [7]

Answer:2.45 m/s

Explanation:

Given

Launch velocity(u)=3 m/s

launch angle=35^{\circ}

as the vertical velocity first decreasing to zero and then increases to original value so its avg is zero .

v_{avg}=\frac{displacement}{time}

v_{avg}=\frac{Range}{time}

v_{avg}=\frac{u\cos \theta \times t}{t}

thus v_{avg}=\frac{3\cos 35\times t}{t}

v_{avg}=3\cos 35=2.45 m/s

8 0
3 years ago
The froghopper Philaenus spumarius is supposedly the best jumper in the animal kingdom. To start a jump, this insect can acceler
Kay [80]

Answer:

Part a)

v_f = 4 m/s

Part b)

t = 0.001 s

Part c)

d = 0.815 m

Explanation:

Part a)

As we know that initially the grass hopper is at rest at the ground position

Now the acceleration is given as

a = 4000 m/s^2

distance of the legs that it stretched is given as

s = 2.0 mm

so we have

v_f^2 - v_i^2 = 2 a d

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Part b)

time taken to reach this speed is given as

v_f - v_i = at

4 - 0 = 4000 t

t = 0.001 s

Part c)

as the grass hopper reach the maximum height its final speed would be zero

so we will have

v_f^2 - v_i^2 = 2 a d

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d = 0.815 m

5 0
3 years ago
Why is the unit of velocity called derived unit ?​
navik [9.2K]

Answer:

Explanation:

The general consensus is that it's more “natural” to define distance (meter) and time (second) and as base units, and derive velocity a the ratio between them. ... The general consensus is that it's more “natural” to define distance (meter) and time (second) and as base units, and derive velocity a the ratio between them.

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3 years ago
What two quantities are always conserved in a nuclear reaction equation?
kupik [55]

Answer:B

Explanation:

Option A:

In the nuclear reactions,neutron can be split into proton an electron.

In this case,the  number of protons are increasing,increasing the atomic number.

Hence,the atomic number is not conserved.

Option B:

In any reaction the sum of number of neutrons and number of protons remain constant before and after the reaction.

Option C:

The mass number may change for the atoms.For example \alpha emission reduces the atomic number by 2.

Option D:

In the nuclear reactions,neutron can be split into proton an electron.

So,they number of neutrons may change.

7 0
2 years ago
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