Question

A 4kg bird has 8 joules of kinetic energy, how fast is it flying?

Answer 1

I believe the answer is 2m/s

Answer 2

Answer:

The bird is flying at a velocity of $v=2\frac{m}{s}$

Explanation:

You should use the equation for the kinetic energy, that is:

$K_{E}=\frac{1}{2}mv^{2}$

where $K_{E}$ is the kinetic energy, m is the mass of the bird and v is its velocity.

Solving for v:

$mv^{2}=2K_{E}$

$v^{2}=\frac{2K_{E}}{m}$

$v=\sqrt{\frac{2K_{E}}{m}}$

And replacing the values given in the problem you have:

$v=\sqrt{\frac{2*8J}{4kg}}$

$v=\sqrt{\frac{16J}{4kg}}$

$v=\sqrt{4\frac{m^{2}}{s^{2}}}$

$v=2\frac{m}{s}$