Question

The car is driving down the road with a kinetic energy of 56J. What is its new kinetic energy now if its velocity is doubled?

Answer 1

Answer:

The new kinetic energy is 224 J

Explanation:

Recall that kinetic energy is defined as: $\frac{1}{2} m\, v^2$  where m is the mass of the object and v its velocity. So the initial situation is that the car has a kinetic energy equal to 56 J when its velocity is "v". Therefore, at this initial velocity, the kinetic energy of the car is;

$\frac{1}{2} m\,v^2 = 56\, J$

in the new new situation, the car has doubled its velocity: from $v$ went to $2v$, without any change in its mass. This means that its new kinetic energy is now given by:

$Knew=\frac{1}{2} m\, (2v)^2=\frac{1}{2} m\, 4 \,v^2= 4 * (\frac{1}{2} m\, v^2)$

which is four times its initial kinetic energy. That is: 4 * 56 J = 224 J