Answer to Question #151169 in Mechanics | Relativity for Rob

Question

A car that is traveling down a highway has
1,30 x 10s J of kinetic energy. A truck with 8.30
times the mass of the car is traveling at the same
speed. What is the kinetic energy of the truck

Answer 1

Let's denote $E =1.3 \times10 \,J = 13 J$

$m_1$ - mass of the car, $m_2$ - mass of the truck. Also, $\frac{m_2}{m_1} =8.3$ and $v_1 = v_2$.

The kinetic energy of the body is

$\displaystyle E = \frac{mv^2}{2}$

$\displaystyle \frac{E_2}{E_1} = \frac{m_2v_2^2}{m_1v_1^2} = \frac{m_2}{m_1} =8.3$

So, $E_2 = 8.3 E_1 = 8.3 \cdot 13 = 107.9 \, J$

Answer: 107.9 J