A bird flying at a height of 12 meters doubles its speed as it descends to a height of 6 meters. The kinetic energy has changed by a factor of: a) 2 b) 4 c) 1 d) 0.25
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Answered on
b) 4
The kinetic energy (KE) of an object is given by the equation:
KE = 1/2 m v^2
Where: m = mass of the object v = velocity of the object
When the bird doubles its speed (velocity), we must square this change to understand how the kinetic energy changes, because the velocity term in the kinetic energy equation is squared.
Let's say the original speed is v. When it doubles, the new speed becomes 2v.
Original kinetic energy (KE₁) = 1/2 m v^2 New kinetic energy (KE₂) = 1/2 m (2v)^2 = 1/2 m 4v^2 = 4 * (1/2 m v^2)
KE₂ is four times KE₁.
Therefore, when a bird doubles its speed, its kinetic energy changes by a factor of 4.