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TiliK225 [7]
2 years ago
6

Bill leaves his 60 W desk lamp on every day, including weekends, for eight hours. After one month (30 days), how much total ener

gy has been used by the lamp? Round your answer to the nearest whole number. kWh
Physics
1 answer:
maxonik [38]2 years ago
7 0

' W ' is the symbol for 'Watt' ... the unit of power equal to 1 joule/second.

That's all the physics we need to know to answer this question.
The rest is just arithmetic.

(60 joules/sec) · (30 days) · (8 hours/day) · (3600 sec/hour)

= (60 · 30 · 8 · 3600) (joule · day · hour · sec) / (sec · day · hour)

= 51,840,000 joules
__________________________________

Wait a minute !  Hold up !  Hee haw !  Whoa ! 
Excuse me.  That will never do.
I see they want the answer in units of kilowatt-hours (kWh).
In that case, it's

(60 watts) · (30 days) · (8 hours/day) · (1 kW/1,000 watts)

= (60 · 30 · 8 · 1 / 1,000) (watt · day · hour · kW / day · watt)

= 14.4 kW·hour

Rounded to the nearest whole number:

14 kWh

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Each plate of an air-filled parallel-plate capacitor has an area of 45.0 cm2, and the separation of the plates is 0.080 mm. A ba
maw [93]

Answer:

Option (e)

Explanation:

A = 45 cm^2 = 0.0045 m^2, d = 0.080 mm = 0.080 x 10^-3 m,

Energy density = 100 J/m

Let Q be the charge on the plates.

Energy density = 1/2 x ε0 x E^2

100 = 0.5 x 8.854 x 10^-12 x E^2

E = 4.75 x 10^6 V/m

V = E x d

V = 4.75 x 10^6 x 0.080 x 10^-3 = 380.22 V

C = ε0 A / d

C = 8.854 x 10^-12 x 45 x 10^-4 / (0.080 x 10^-3) = 4.98 x 10^-10 F

Q = C x V = 4.98 x 10^-10 x 380.22 = 1.9 x 10^-7 C

Q =  190 nC

3 0
3 years ago
Suppose a wheel with a tire mounted on it is rotating at the constant rate of 2.83 times a second. A tack is stuck in the tire a
timama [110]

Answer:

The tangential speed of the tack is 6.988 meters per second.

Explanation:

The tangential speed experimented by the tack (v), measured in meters per second, is equal to the product of the angular speed of the wheel (\omega), measured in radians per second, and the distance of the tack respect to the rotation axis (R), measured in meters, length that coincides with the radius of the tire. First, we convert the angular speed of the wheel from revolutions per second to radians per second:

\omega = 2.83\,\frac{rev}{s} \times \frac{2\pi\,rad}{1\,rev}

\omega \approx 17.781\,\frac{rad}{s}

Then, the tangential speed of the tack is: (\omega \approx 17.781\,\frac{rad}{s}, R = 0.393\,m)

v = \left(17.781\,\frac{rad}{s} \right)\cdot (0.393\,m)

v = 6.988\,\frac{m}{s}

The tangential speed of the tack is 6.988 meters per second.

7 0
2 years ago
A vector has an x-component
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Explanation:

The magnitude of a vector v can be found using Pythagorean's theorem.

||v|| = √(vₓ² + vᵧ²)

||v|| = √((-309)² + (187)²)

||v|| ≈ 361

You can find the angle of a vector using trigonometry.

tan θ = vᵧ / vₓ

tan θ = 187 / -309

θ ≈ 149° or θ ≈ 329°

vₓ is negative and vᵧ is positive, so θ must be in the second quadrant.  Therefore, θ ≈ 149°.

4 0
3 years ago
A pendulum with a mass of 250 g is released from its maximum displacement of 5 degrees and swings with a simple harmonic motion.
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L=T2xg/4x3.14^2
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