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kramer
2 years ago
13

To practice Problem-Solving Strategy 25.1 Power and Energy in Circuits. A device for heating a cup of water in a car connects to

the car's battery, which has an emf E = 10.0 V and an internal resistance rint = 0.04 Ω . The heating element that is immersed in the cup of water is a resistive coil with resistance R. David wants to experiment with the device, so he connects an ammeter into the circuit and measures 12.0 A when the device is connected to the car's battery. From this, he calculates the time to boil a cup of water using the device. If the energy required is 100 kJ , how long does it take to boil a cup of water?
Physics
1 answer:
jeyben [28]2 years ago
4 0

Answer:

The time to boil the water is 877 s

Explanation:

The first thing we must do is calculate the external resistance (R) of the circuit, from the description we notice that it is a series circuit, by which the resistors are added

    V = i (r + R)

We replace we calculate

     r + R = V / i

     R = v / i - r

     R = 10/12 -0.04

     R = 0.793 Ω

We calculate the power supplied

     P = V i = I² R

     P = 12² 0.793

     P = 114 W

This is the power dissipated in the external resistance

We use the relationship, that power is work per unit of time and that work is the variation of energy

     P = E / t

     t = E / P

     t = 100 10³/114

     t = 877 s

The time to boil the water is 877 s

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Assuming the pick-up trucks, trailers and road conditions are exactly the same, which vehicle will take a longer distance to sto
mars1129 [50]

I’ve answered this before so I know the question is missing an important given and that given is: <span>1 has an empty trailer and the other has a fully loaded one. 

So, it would be the fully loaded trailer that would take a longer distance to stop because a lot of weight is being pulled, and when the brakes are started, the fully loaded trailer is more like pushing against the truck.</span>

6 0
1 year ago
You are a member of a geological team in Central Africa. Your team comes upon a wide river that is flowing east. You must determ
Dovator [93]

Answer:

(a). The width of the river is 90.5 m.

The current speed of the river is 3.96 m.

(b). The shortest time is 15.0 sec and we would end 59.4 m east of our starting point.

Explanation:

Given that,

Constant speed = 6.00 m/s

Time = 20.1 sec

Speed = 9.00 m/s

Time = 11.2 sec

We need to write a equation for to travel due north across the river,

Using equation for north

v^2-c^2=\dfrac{w^2}{t^2}

Put the value in the equation

6.00^2-c^2=\dfrac{w^2}{(20.1)^2}

36-c^2=\dfrac{w^2}{404.01}....(I)

We need to write a equation for to travel due south across the river,

Using equation for south

v^2-c^2=\dfrac{w^2}{t^2}

Put the value in the equation

9.00^2-c^2=\dfrac{w^2}{(11.2)^2}

81-c^2=\dfrac{w^2}{125.44}....(II)

(a). We need to calculate the wide of the river

Using equation (I) and (II)

45=\dfrac{w^2}{125.44}-\dfrac{w^2}{404.01}

45=w^2(0.00549)

w^2=\dfrac{45}{0.00549}

w=\sqrt{\dfrac{45}{0.00549}}

w=90.5

We need to calculate the current speed

Using equation (I)

36-c^2=\dfrac{(90.5)^2}{(20.1)^2}

36-c^2=20.27

c^2=20.27-36

c=\sqrt{15.73}

c=3.96\ m/s

(b). We need to calculate the shortest time

Using formula of time

t=\dfrac{d}{v}

t=\dfrac{90.5}{6}

t=15.0\ sec

We need to calculate the distance

Using formula of distance

d=vt

d=3.96\times15.0

d=59.4\ m

Hence, (a). The width of the river is 90.5 m.

The current speed of the river is 3.96 m.

(b). The shortest time is 15.0 sec and we would end 59.4 m east of our starting point.

3 0
2 years ago
A uniform ladder 15 ft long is leaning against a frictionless wall at an angle of 53 above the horizontal. the weight of the la
arsen [322]
<h3><u>Answer;</u></h3>

33.9 pounds

<h3><u>Explanation</u>;</h3>

In order for the ladder to be in equilibrium, the net torque should be equal to zero. Therefore, the torque in the opposite directions should equal each other:

Clockwise torque = Counter clockwise torque

Torque is the product of the applied force and the distance between that force and the axis of rotation.

Wι (7.5 ft) cos 53° + Wb (6 ft) cos 53° = F (15 ft) sin 53 °

Substitute the values for the weights of the ladder and the boy, respectively.

(20 lb) (7.5 ft)cos 53° + (75 lb) (6 ft) cos 53° = F(15 ft) sin 53°

Solving for F;

F = ((30 ×7.5 × cos 53°) + (75 × 6 × cos 53°))/ (15 × sin 53°)

  = 33.9 lb

  <u>= 33.9 Pounds</u>

4 0
2 years ago
A 6.00-m long rope is under a tension of 600 N. Waves travel along this rope at 40.0 m/s. What is the mass of the rope?
MAVERICK [17]

Answer:

2.25 kg

Explanation:

Length, L = 6 m

tension, T = 600 N

velocity, v = 40 m/s

The formula for the velocity is given by

v=\sqrt{\frac{T}{\mu }}

where, μ is mass per unit length

\mu =\frac{T}{v^{2}}

\mu =\frac{600}{40^{2}}

μ = 0.375

m / L = 0.375

m = 0.375 x 6 = 2.25 kg

Thus, the mass of rope is 2.25 Kg.

6 0
1 year ago
A flat surface is in a uniform magnetic field. Given only the area of the surface and the magnetic flux through the surface, it
Tasya [4]

Answer:

Given the area A of a flat surface and the magnetic flux through the surface \Phi it is possible to calculate the magnitude \frac{\Phi}{A}=B\ cos \theta.

Explanation:

The magnetic flux gives an idea of how many magnetic field lines are passing through a surface. The SI unit of the magnetic flux \Phi is the weber (Wb), of the magnetic field B is the tesla (T) and of the area A is (m^{2}). So 1 Wb=1 T.m².

For a flat surface S of area A in a uniform magnetic field B, with \theta being the angle between the vector normal to the surface S and the direction of the magnetic field B, we define the magnetic flux through the surface as:

                                                     \Phi=B\ A\ cos\theta

We are told the values of \Phi and B, then we can calculate the magnitude

                                                      \frac{\Phi}{A}=B\ cos\theta

3 0
1 year ago
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