I would say Option B) because Option C) is wrong since matter cannot be created. A closed system does not exchange matter so it's not Option D). Since an island is an isolated area, Option A) is wrong.
The emerging velocity of the bullet is <u>71 m/s.</u>
The bullet of mass <em>m</em> moving with a velocity <em>u</em> has kinetic energy. When it pierces the block of wood, the block exerts a force of friction on the bullet. As the bullet passes through the block, work is done against the resistive forces exerted on the bullet by the block. This results in the reduction of the bullet's kinetic energy. The bullet has a speed <em>v</em> when it emerges from the block.
If the block exerts a resistive force <em>F</em> on the bullet and the thickness of the block is <em>x</em> then, the work done by the resistive force is given by,

This is equal to the change in the bullet's kinetic energy.

If the thickness of the block is reduced by one-half, the bullet emerges out with a velocity v<em>₁.</em>
Assuming the same resistive forces to act on the bullet,

Divide equation (2) by equation (1) and simplify for v<em>₁.</em>

Thus the speed of the bullet is 71 m/s
Answer:
3,544.375Joules
Explanation:
Kinetic energy is the energy possessed by a body by virtue of its motion, It is expressed as;
Kinetic energy = 1/2mv²
m is the mass of the body
v is the velocity
For the ball carrier;
KE = 1/2(75)(6.5)²
KE = 3168.75/2
KE = 1584.375Joules
For the defender;
KE = 1/2(80)(7)²
KE = 3920/2
KE = 1960Joules
The kinetic energy of the ball carrier/defender system BEFORE the tackle = KE for the carrier + KE for the defender
kinetic energy of the ball carrier/defender system BEFORE the tackle= 1584.375+1960 = 3,544.375Joules
Answer:
Its called the hydrosphere UwU!
Explanation: