A 30 kg kid on rollerskates is moving 1 m/s. His brother pushes him with a force of 5N. What will be his kinetic energy after his brother pushes him 4.0m. (I'm not sure what equation/formula to use)

Question

A 30 kg kid on rollerskates is moving 1 m/s.  His brother pushes him with a force of 5N.  What will be his kinetic energy after his brother pushes him 4.0m.  (I'm not sure what equation/formula to use)

anonymous · Answer

What Are We Looking For (WALF):
The answer to:
$$K=\frac{1}{2}mv^2$$
To do this, we need the values of mass (which the question has given us) and velocity (which we will obtain)

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So we have:
$$m=30kg ,and, v_0=1\frac{m}{s}$$
His brother gives him a push:
$$F=ma$$
So we can say:
$$(5N)=(30kg)(a)$$
We calculate acceleration as:
$$a=\frac{1}{6}$$

We now have the square of the velocity and mass: can you give the answer?
Using
$$v^2=2a(\Delta x)+v^2_0$$
We can find out the speed at at 4 meters.
So
$$v^2=2(\frac{1}{6})(4-0)+1^2$$
$$v^2=\frac{7}{3}$$