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Lana71 [14]
3 years ago
11

David wants to experiment with the device, so he connects an ammeter into the circuit and measures 11.5 AA when the device is co

nnected 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 kJkJ , how long does it take to boil a cup of water?
Physics
1 answer:
Mandarinka [93]3 years ago
4 0

Answer:

2.42hours

Explanation:

To calculate the time taken to boil the cup of water, we will use the formula

Q = It where

Q is the total energy required to boil the water = 100KJ = 100,000Joules

I is the current = 11.5A

t is the time taken to boil the water

t = Q/I

t = 100,000/11.5

t = 8695.65seconds

t = 2.42hours

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A string with a mass density of 3 * 10^-3 kg/m is under a tension of 380 N and is fixed at both ends. One of its resonance frequ
Delvig [45]

Answer:

(a) the fundamental frequency of this string is 65 Hz

(b) the harmonics of the given frequencies are third and fourth respectively.

(c) the length of the string is 2.74 m

Explanation:

Given;

mass density of the string, μ = 3 x 10⁻³ kg/m

tension of the string, T = 380 N

resonating frequencies, 195 Hz and 260 N

For the given resonant frequencies;

195 = \frac{n}{2l} \sqrt{\frac{T}{\mu} } ---(1)\\\\260 = \frac{n+1}{2l} \sqrt{\frac{T}{\mu} } ---(2)\\\\divide \ (2) \ by (1)\\\\\frac{260}{195} = \frac{n+1 }{n} \\\\260n = 195(n+1)\\\\260 n = 195 n + 195\\\\260n - 195n = 195\\\\65n = 195\\\\n = \frac{195}{65} \\\\n = 3

(c) From any of the equations, solve for Length of the string (L);

195 = \frac{n}{2l} \sqrt{\frac{T}{\mu} } \\\\195 = \frac{3}{2l}\sqrt{\frac{380}{3\times 10^{-3}} } \\\\l = \frac{3}{2\times 195}\sqrt{\frac{380}{3\times 10^{-3}} }\\\\l = 2.74 \ m

(a) the fundamental frequency is calculated as;

f_o = \frac{1}{2l} \sqrt{\frac{T}{\mu} } \\\\f_o = \frac{1}{2\times 2.74} \sqrt{\frac{380}{3\times 10^{-3} } }\\\\f_o =  65 \ Hz

(b) harmonics of the given frequencies;

the first harmonic (n = 1) = f₀ = 65 Hz

the second harmonic (n = 2) = 2f₀ = 130 Hz

the third harmonic (n = 3) = 3f₀ = 195 Hz

the fourth harmonic (n = 4) = 4f₀ = 260 Hz

Thus, the harmonics of the given frequencies are third and fourth respectively.

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The hour, minute, and second hands on a clock are 0.25 m , 0.31 m , and 0.34 m long, respectively.
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In 1 hour, the hour hand sweeps across 1/12 of the clock's face. In 40 min, the hour hand travels (40 min)/(60 min) = 2/3 of the path it covers in an hour, so a total of 1/12 × 2/3 = 1/18 of the clock's face. This hand traces out a circle with radius 0.25 m, so in 40 min its tip traces out 1/18 of this circle's radius, or

1/18 × 2<em>π</em> (0.25 m) ≈ 0.087 m

The minute hand traverses (40 min)/(60 min) = 2/3 of the clock's face, so it traces out 2/3 of the circumference of a circle with radius 0.31 m:

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The second hand completes 1 revolution each minute, so in 40 min it would fully trace the circumference of a circle with radius 0.34 m a total of 40 times, so it covers a distance of

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Define measurement What problems might me face it measurement systems were not established? (1+2=3) ​
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Answer:

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If a gun is sighted to hit targets that are at the same height as the gun and 75 m away at the same height, how low, as a positi
Vinvika [58]

Answer:

y=-1.66 m

Explanation:

   We know that

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R=\dfrac{u^2sin2\theta }{g}

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Now by putting the values

R=\dfrac{u^2sin2\theta }{g}

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Now horizontal component of velocity u will be u cosθ.

Horizontal component = 275 cos0.13 = 274.99 m/s

So the time required to cover 180 m in horizontal direction t

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Now vertical component of velocity u will be u sinθ.

Horizontal component = 275 sin0.13 = 0.62 m/s

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