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
Sunlight, because it provides a source of energy is the answer because plants also provide a food source (please put as brainliest answer)
Given, mass of titanium metal = 144 g
Heat of fusion of titanium metal= 18.7 J/g
Heat of fusion is the amount of heat energy needed to change the state of one gram of a substance from solid to liquid or vice-versa.
Thus, 18.7 J of heat is needed to melt one gram of titanium metal.
Therefore, heat needed to melt 144 g of titanium metal = 18.7×144
= 2692.8 J
Answer:
Sorry @Josh2013, the answer is B. heart beating.
Explanation:
The reason for this answer is heart beating is an involuntary action, it happens on it's own. Eating, sleeping, and crying are all voluntary actions. And a behavior is an action you do voluntarily.