The US Department of Energy has set its own targets to achieve 15% of the country's electricity from hydropower by 2030 — it is currently 7%. Elsewhere around the world, countries are pledging to meet more and more of their energy needs through renewable energy sources.
Answer:
773.25 Hz
Explanation:
Concept : In an open organ pipe in fundamental mode of vibration
wave length of wave λ = 2L
where L is length of the pipe
frequency = velocity of sound / λ
Given values: fundamental frequency = 288 Hz
fluid is air. velocity of sound = 340 m/s
⇒ 288 = 340/2L
⇒L = 59.02 cm
The point to be noted is if the pipe is filled with helium initially at the same temperature, there would be change in the sound velocity .Then, frequency of note produced will also be changed .
We know that velocity of sound is inversely proportional to square root of molar mass of gas
velocity of sound in air / velocity of sound in helium = Square root of (Molar mass of Helium/ molar mass of air)

Now, frequency = velocity of sound / λ
= 912.75 / (2 x 0.5902)
= 773.25 Hz
Answer:
Energy
Explanation:
One ways of stating the law of conservation of energy is that "you cannot get more energy from a machine than the amount of energy you put into it".
The law of conservation of energy states that in a system, energy is neither created nor destroyed but transformed from one form to another.
The energy in a system does not increase based on the premise of this law.
- The efficiency of a machine can reduce but the energy is always conserved.
- This is because energy is transformed to other forms.
Answer:
15 deg
Explanation:
Assume both snowballs are thrown with the same initial speed 27.2 m/s. The first snowball is thrown at an angle of 75◦ above the horizontal. At what angle should you throw the second snowball to make it hit the same point as the first? The acceleration of gravity is 9.8 m/s 2 . Answer in units of ◦ .
Given:
For first ball, θ1 = 75◦
initial velocity for both the balls, u = 27.2 m/s
for second ball, θ2 = ?
since distance covered by both the balls is same.
Therefore,..
R1=(u^{2} sin2\alpha _{1}) /g[/tex]
the range for the first ball
the range for the second ball
R2=(u^{2} sin2\alpha _{2}) /g[/tex]
(u^{2} sin2\alpha _{2}) /g[/tex]=(u^{2} sin2\alpha _{1}) /g[/tex]
sin2\alpha _{2})=sin2\alpha _{1})
=sin^-1(sin2\alpha _{1})
=1/2sin^-1(sin2\alpha _{1})
=
15 deg