Question

A toy car is moving along with 0.40 J of kinetic energy. If thespeed is doubled, what will the new kinetic energy be?

Answer 1

Given the Kinetic energy of a toy car, K.E.=04.J

To find new Kinetic energy, K.E.' when speed is doubled.

Kinetic energy is given by the formula,

$K\mathrm{}E\mathrm{}=\frac{1}{2}mv^2$

Here, m is the mass and v is the speed.

Now, if the new speed v'=2v, then new kinetic energy will be

$\begin{gathered} KE^{\prime}=\frac{1}{2}mv^{\prime2} \\ \end{gathered}$

$\begin{gathered} K\mathrm{}E\mathrm{}^{\prime}=\frac{1}{2}m(2v)^2 \\ =\frac{1}{2}m\times4v^2 \\ =4\times\frac{1}{2}mv^2 \\ =4\times K.E. \end{gathered}$

Substituting the value of K.E. in the above equation, we get

$\begin{gathered} K\mathrm{}E\mathrm{}^{\prime}=4\times0.4 \\ =1.6\text{ J} \end{gathered}$

Thus, the new kinetic energy will be 4 times of initial kinetic energy and its value will be 1.6 J when speed is doubled.