Question: How fast was the arrow moving before it joined the block?
Answer:
The arrow was moving at 15.9 m/s.
Explanation:
The law of conservation of energy says that the kinetic energy of the arrow must be converted into the potential energy of the block and arrow after it they join:
where 
is the mass of the arrow, 
is the mass of the block, 
of the change in height of the block after the collision, and 
is the velocity of the arrow before it hit the block.
Solving for the velocity , we get:
and we put in the numerical values
,
and simplify to get:
The arrow was moving at 15.9 m/s
Cause: sewage dumped in rivers,disease spread, and industrial waste dumped into rivers
Effect: fish die off, destroyed habitats, oil spills on land that mixes with run off
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Answer:
2649600 Joules
Explanation:
Efficiency = 40%
m = Mass of air = 92000 kg
v = Velocity of wind = 12 m/s
Kinetic energy is given by
The kinetic energy of the wind is 6624000 Joules
The wind turbine extracts 40% of the kinetic energy of the wind
The energy extracted by the turbine every second is 2649600 Joules
