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sashaice [31]
3 years ago
7

In a 120-volt circuit having a resistance of 12 ohms, the power W in watts when a current I is flowing through is given by W=120

I−12I². What is the maximum power, in watts, that can be delivered in this circuit?
Physics
1 answer:
Mrac [35]3 years ago
5 0

Answer:

maximum power = 300 W

Explanation:

Ohm's law: Ohm's law state that the current flowing through a metallic conductor, is directly proportional to the potential difference applied across its end. mathematically it is expressed as,

V = IR............. Equation 1

Where V = potential difference, I = current, R = Resistance of the conductor.

If the power flowing through is gives as

W = 120I - 12I² ..................... Equation 2

To get the maximum power we differentiate of equation 2  and equate to zero

dW/dt = 0

120 - 24l = 0........................... equation 3

Making I the subject of the equation,

I = 120/24 = 5 A.

Suubstituting the value of I into Equation 2

W = 120 (5) - 12(5)²

W = 600 - 300

W = 300 W.

Therefore maximum power = 300 W

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An internal combustion engine uses fuel, of energy content 44.4 MJ/kg, at a rate of 5 kg/h. If the efficiency is 28%, determine
Fudgin [204]
Efficiency =  Power Output / Power Input

Power Input = Rate of Energy input = 44.4 MJ/kg * 5 kg/h

 = 222 MJ/h

But 1 hour = 3600seconds

222 MJ/h = 222 MJ/3600s =  0.061667 MW              J/s = Watts

Power input = 0.061667 MW = 61 667 W

From  Efficiency =  Power Output / Power Input

   28% =  Power Output / 61667

   Power Output = 0.28 * 61667

   Power Output = 17266.76 W
 
  Power Output = 17 267 W

 Rate of heat Rejection = Power input - Power output

                                        = 61667 - 17267 = 44400 W

Rate of heat Rejection = 44 400 W.


C- Copyright.
5 0
3 years ago
Objects fall near the surface of the earth with a constant downward acceleration of 10 m/s2 . Suppose a falling object is moving
Papessa [141]

Answer:

The final velocity of the object after 2 seconds is 30 m/s

Explanation:

Given;

constant downward acceleration, a =  10 m/s²

initial velocity of the object falling down, v = 10 m/s

time of fall, t = 2 s

The final velocity of the object is given by;

v = u + at

where;

v is the final velocity

v = 10 + (10)(2)

v = 10 + 20

v = 30 m/s

Therefore, the final velocity of the object after 2 seconds is 30 m/s

3 0
2 years ago
You have gas in a container with a movable piston. The walls of the container are thin enough so that its temperature stays the
bearhunter [10]

Answer:

New pressure of the gas increases by 26.5% with respect to initial pressure, new volume decreases 27% with respect to initial volume and new temperature decreases 8% with respect to initial volume.

Explanation:

If we assume the gas is a perfect gas we can use the perfect gas equation:

PV=nRT

  • For Isothermal process:

\frac{P_{1}V_{1}}{T_{1}}=\frac{P_{2}V_{2}}{T_{2}}(1)

Where subscripts 1 shows before the isothermal process and 2 after it, because isothermal means constant temperature T1=T2, and pressure increases by 10% means P2=1,1*P1, using these facts on (1) we have:

V_{2}=\frac{V_{1}}{1.1} (2)

  • For Isobaric process:

\frac{P_{2}V_{2}}{T_{2}}=\frac{P_{3}V_{3}}{T_{3}} (3)

Where subscripts 2 shows before the isobaric process and 3 after it, because isobaric means constant pressure P2=P3, and volume decreases by 20% means V3=0.8*V2, using these facts on (3) we have:

T_{3}=0.8T_{2} (4)

  • For Isochoric process:

\frac{P_{3}V_{3}}{T_{3}}=\frac{P_{4}V_{4}}{T_{4}} (5)

Where subscripts 3 shows before the isochoric process and 4 after it, because isochoric means constant volume V3=V4, and temperature increases by 15% means T4=1.15*T3, using these facts on (5) we have:

P_{4}=1.15P_{3} (6)

So now because P4=1.15*P3, P2=P3 and P2=1.1*P1:

P_{4}=1.15*1.1P_{1}=1.265P1

This is, the new pressure of the gas increases by 26.5%  with respect to initial pressure.

Similarly, we have V3=V4, V3=0.8*V2 and V1=1,1*V2:

V_{4}=\frac{0.8}{1.1}V_{1}=0.72V1

so the final volume decreases 27% with respect to initial volume.

T4=1,15*T3, T3=0.8*T2 and T1=T2:

T_{4}=1.15*0.8T_{1}=0.92T1

The new temperature decreases 8% with respect to initial volume.

3 0
3 years ago
SY19-
vovangra [49]

Answer:Net force/mass

Explanation:

7 0
3 years ago
3. A worker pushes a box across the floor to the right at a constant speed with a force of 25N. What
WITCHER [35]

Answer:

Friction between the box and the floor is 25N to the left.

Explanation:

According to Newton's second law of motion, the net force acting on an object is equal to the produce between the object's mass and its acceleration:

F_{net}=ma

where

m is the mass of the object

a is its acceleration

In this problem, we have two forces acting on the object:

- The applied force, F = 25 N, to the right

- The force of friction F_f, opposing the motion of the box, so to the left

So we can write the net force as

F_{net}=F-F_f

Also, we know that the box is moving at constant speed: this means its acceleration is zero, so

a=0

Therefore

F_{net}=0

WHich means:

F-F_f=0

And therefore,

F_f=F=25 N

which means that the force of friction is also 25 N.

6 0
3 years ago
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