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3 years ago

a electric fire is connected to the city power grid (120 V) it draws a current of 6A what is its power rating?

Physics

1 answer:

trapecia [35]3 years ago

4 0

Answer:

720 Watts

Explanation:

Given:

Voltage (V) = 120 V
Current (I) = 6A

To Find:

Power (P)

Solution:

We know that electrical power is product of Voltage and current. So, Power formula is given by:

$\\ \: \: \: \dashrightarrow \sf \: \: \: \underline{\boxed{\sf{ Power = Voltage \times Current}}} \\ \\$

On substituting the required values, we get:

$~~~\dashrightarrow~~~~$ Power = 120 V × 6 A

$~~~\dashrightarrow~~~~$ Power = 720 watts

Hence,

Power rating is <u>720 Watts</u>

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A runner starts from rest and in 3 s reaches a speed of 8 m/s. If we assume that the speed changed at a constant rate (constant

Stells [14]

Answer:

The average speed of the runner is 4 m/s.

Explanation:

Hi there!

The average speed (a.s) is calculated by dividing the traveled distance (d) over the time needed to travel that distance (t):

a.s = d / t

So, let´s find the distance traveled in those 3 s. For that, we can use the equation of position of an object moving in a straight line with constant acceleration:

x = x0 + v0 · t + 1/2 · a · t²

Where:

x = position of the object at time t.

x0 = initial position.

v0 = initial velocity.

t = time.

a = acceleration.

If we place the origin of the frame of reference at the point where the runner starts, then, x0 = 0. Since the runner starts from rest, v0 = 0. So, the equation gets reduced to this:

x = 1/2 · a · t²

We have the time (3 s), so let´s find the acceleration. For that, we can use the equation of velocity of an object moving in a straight line with constant acceleration:

v = v0 + a · t

Where "v" is the velocity at a time "t". Since v0 = 0, then:

v = a · t

At t = 3 s, v = 8 m/s

8 m/s = a · 3 s

8/3 m/s² = a

So let´s find the position of the runner at t = 3 s (In this case, the position of the runner will be equal to the traveled distance):

x = 1/2 · a · t²

x = 1/2 · 8/3 m/s² · (3 s)²

x = 12 m

Now, we can calcualte the average speed:

a.s = d/t

a.s = 12 m / 3 s

a.s = 4 m/s

The average speed of the runner is 4 m/s.

4 0

3 years ago

If 190 grams of water is cooled from 42.7°C to 21.2° C how much energy was lost by the water?

yanalaym [24]

Answer:

Energy lost by the water is 17.1 x 10³ J .

Explanation:

Specific heat is defined as the amount of energy per unit mass needed to raise the temperature of the substance by a one degree Celsius.

Heat energy gain or loss by any substance is given by :

Q = m x C x ( T₁ - T₂ ) .....(1)

Here m is the mass of the substance, C is specific heat of the substance and T₁ and T₂ are the initial and final temperature of the substance.

According to the problem,

Mass of water, m = 190 gm

Specific heat of water, C = 4.186 J gm⁻¹ ⁰C⁻¹

Initial temperature, T₁ = 42.7⁰ C

Final temperature, T₂ = 21.2⁰ C

Substitute these values in equation (1).

Heat energy loss by water = 190 x 4.186 x ( 21.2 - 42.7 )

= -17.1 x 10³ J

In the above value, negative sign denotes the loss in energy.

7 0

4 years ago

A car travels at a steady speed of 10 m/s. What distance is covered in a minute?

AfilCa [17]

Answer:

600

Explanation:

8 0

3 years ago

Read 2 more answers

Jeremy walked at an average rate of speed of 3 km/h. How far had Jeremy

makvit [3.9K]

D is the answer and also I love u

8 0

3 years ago

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A person driving her car at 43 km/h approaches an intersection just as the traffic light turns yellow. She knows that the yellow

siniylev [52]

Answer:

If she hits the brakes, she will travel 13m before stopping. If she hits the gas, she will travel 28 before the light turns red. She should try to stop

Explanation:

To know how far she will travel before stopping, we need to use a kinematic formula which initial final velocity (Vf), initial velocity (V0), acceleration (a) and distance traveled(x):

$V_{f}^{2}=V_{0} ^{2} +2ax$

The moment in which she stops is when the final velocity equals zero. In this case, initial velocity is 43km/h=12m/s, and its maximum deceleration is -5.4m/s^2. Plugging in these values and solving for x:

$0^2=(12m/s)^2+2(-5.4m/s)x\\x=13m$

She will travel 13m before stopping

If she hits the gas, we need another kinematic formula, which relates distance traveled, initial speed, time (t) and acceleration.

$x=v_{0}t+0.5a*t^2$

If we know her car can accelerate from 43km/h=12m/s to 70km/h=19m/s in 8.1 s, we can know its acceleration:

$a=\frac{19m/s-12m/s}{8.1s}=0.86m/s^2$

In this case, the time before the light turns red is 2.0s. Plugging in all those values:

$x=12m/s*2s+0.5*0.86m/s^2*(2s)^2=28m$

If she hits the gas, she will travel 28m before the light turns red. She won't even reach the intersection, so she would try to stop.

5 0

3 years ago