Answer:
120,000J
Corrected question;
In one hour, coal supplies 500 000 J of energy. The wasted energy amounts to 380 000 J. How much useful energy is produced in one hour?
Explanation:
Given;
Total energy Et = 500,000 J
Wasted Energy Ew = 380,000J
The amount useful energy is the amount of energy that is available for supply.
This can be derived by subtracting the wasted energy from the total energy.
Useful energy = Total Energy - wasted energy
Eu = Et - Ew
Substituting the given values;
Eu = 500,000J - 380,000
Eu = 120,000 J
The amount of useful energy produced in one hour is 120,000 J
Answer:
10 seconds.
Explanation:
We can use a kinematic equation where we know the final velocity, initial velocity, acceleration, and need to determine the time <em>t: </em>
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The initial velocit is 30 m/s, the final velocity is 0 m/s (as we stopped), and the acceleration is -3 m/s².
Substitute and solve for <em>t: </em>
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Hence, it will take the car 10 seconds to come to a stop.
Answer:
c. You would weigh less on planet A because the distance between
you and the planet's center of gravity would be smaller.
Explanation:
The statement that best describes your weight on each planet is that you would weigh less on planet A because the distance between you and the planet's center of gravity would be smaller.
- This is based on Newton's law of universal gravitation which states that "the force of gravity between two bodies is directly proportional to the product of their masses and inversely proportional to the square of the distances between them".
Since weight is dependent on the force of gravity and mass, the planet with more gravitational pull will have masses on them weighing more.
- Since the distance between the person and the center of the planet is smaller, therefore, the weight will be lesser.
Answer:
Three types of electromagnetic waves, used to transmit various information
Explanation:
A form of energy waves having both electric & magnetic fields are Electromagnetic waves. Three types -
Radio Waves - These have longest wavelengths & transmit data through radio, satellites, radar .
Micro Waves - These have shorter wavelengths & are used in cooking appliances & predicting weather.
X rays - These have more short wavelength and can penerate soft tissues like skin & muscle, hence are used for medical examining
<u>Answer :</u>
(a) d = 0.25 m
(b) d = 0.5 m
<u>Explanation :</u>
It is given that,
Frequency of sound waves, f = 686 Hz
Speed of sound wave at 
is, v = 343 m/s
(1) Perfectly destructive interference occurs when the path difference is half integral multiple of wavelength i.e.
........(1)
Velocity of sound wave is given by :
Hence, when the speakers are in phase the smallest distance between the speakers for which the interference of the sound waves is perfectly destructive is 0.25 m.
(2) For constructive interference, the path difference is integral multiple of wavelengths i.e.
( n = integers )
Let n = 1
So, 
Hence, the smallest distance between the speakers for which the interference of the sound waves is maximum constructive is 0.5 m.
