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QveST [7]
3 years ago
14

A lightbulb has a power of 100 W and is used for 4 hours. A microwave has a power of 1200 W and is used for 5 minutes. How much

energy is used by the lightbulb? How much energy is used by the microwave? The lightbulb has an efficiency of 1.8%. How much heat energy does the lightbulb produce in 4 hours?
Physics
1 answer:
ladessa [460]3 years ago
4 0

Answer:

a. E=1440KJ

b. E=360KJ

c. E=1.8 J

Explanation:

I have the power (Watts) is expressed as Energy (Joules) / Time (seconds), also I have to1hour * \frac{60min}{1hour}*\frac{60s}{1min}\\1h=3600s

so, for the lightbulb

100W= \frac{Energy}{3600s*4}\\Energy=100W*14400s\\ E=1440000J =1440KJ

Analogously, for the microwave

1200W= \frac{Energy}{60s*5}\\Energy=1200W*300s\\ E=360000J =360KJ

Now, I have to express the efficiency as Heat energy / power * 100 so1.8= \frac{Heat Energy}{100W}*100\\Heat Energy=1.8J

Done

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The average diameter of one tennis ball in a package of three is 6.8 cm. Which of the following is the combined volume of all th
Crank

We want to find the combined volume of 3 tennis balls. We will get that the combined volume is 493.7 cm^3

First, remember that for a sphere of diameter D, the volume is:

V = \frac{4}{3}*3.14*(\frac{D}{2})^3

Where 3.14 is pi.

Here we know that the average diameter of a tennis ball is 6.8cm, then we can replace that in the above equation to find the volume (in average) of a single tennis ball:

V = \frac{4}{3}*3.14*(\frac{6.8cm}{2})^3 = 164.5 cm^3

Now, in 3 balls of tennis, the combined volume will be 3 times the above one, this is:

3*V = 3*164.5cm^3 = 493.7 cm^3

If you want to learn more about volumes, you can read:

brainly.com/question/10171109

4 0
2 years ago
A toy cannon launches a 46-g golf ball straight up into the air with a kinetic energy of 6.8 J. What must the
Shkiper50 [21]

Answer : The correct option is, (C) 17 m/s

Explanation :

Formula used :

K.E=\frac{1}{2}mv^2

where,

K.E = kinetic energy = 6.8 J

m = mass of object = 46 g = 0.046 kg    (1 kg = 1000 g)

v = velocity

Now put all the given values in the above formula, we get:

K.E=\frac{1}{2}mv^2

6.8J=\frac{1}{2}\times 0.046kg\times v^2

6.8kg.m^2/s^2=\frac{1}{2}\times 0.046kg\times v^2

v=17.19m/s\approx 17m/s

Therefore, the ball's velocity be as it leaves the cannon is, 17 m/s

3 0
3 years ago
C
mestny [16]

Answer:

kftisgkstisirstizurzursrus

3 0
3 years ago
A car accelerate from 25m/s to 50m/s over a time of 10 second.what is acceleration of the car
Ann [662]
A=(vf-vi)/t
a=(50-25)/10
a=2.5m/s^2
5 0
3 years ago
The coefficient of linear expansion of steel is 12 × 10-6 K-1 . What is the change in length of a 25-m steel bridge span when it
Westkost [7]

Answer:

0.012-m

Explanation:

∆L = α × Lo × (T-To)

α is the coefficient of linear expansion = 12 × 10-6 K-1

Lo = Initial length = 25-m

∆L = Change in length

(T-To) = 40 K

∆L = 12 × 10-6 × 25 × 40

∆L = 0.012-m

4 0
3 years ago
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