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
The circumference of a circle is (pi) x (diameter)
The circumference of the cupcake is (pi) x (5 cm)
Halfway around is (1/2) x (pi) x (5 cm) = (2.5 pi cm) = <em>about 7.85 cm</em>
The 'why' appears up above, in the first 2 lines of this solution.
A uranium-235 atom<span> absorbs a neutron and fissions into two new </span>atoms<span> (fission fragments), releasing three new neutrons and some binding energy. ... Several heavy elements, such as uranium, thorium, and plutonium, undergo both spontaneous fission, a form of radioactive decay and induced fission, a form of </span>nuclear<span> reaction.</span>
It must exist in p<span>lasma state.</span>
5) 204 meters
6)
A) 150 miles
B)241 km
