Concerning 83022

A man with a mass of 80 kg crosses at a speed of 5 m/s through the car of a train traveling at 15 m/s. Indeed, the kinetic energy of a man:
and, concerning the car
b, relative to the surface of the earth, if the man is traveling in the direction of travel of the train
c, relative to the surface of the earth, if the man is traveling in the opposite direction of the train

Correct answer:

E₁ =  1000 J
E₂ =  16000 J
E₃ =  4000 J

Step-by-step explanation:

$$\begin{gathered} r_1=15\text{m/s} \\ {r}_2=5\text{m/s} \\ m=80\text{kg} \\ {v}_1=r_2=5\text{m/s} \\ {E}_1=\frac{1}{2}\cdot m\cdot v_1^2=\frac{1}{2}\cdot 80\cdot 5^2=1000\text{J} \end{gathered}$$

$$\begin{gathered} v_2=r_1+r_2=15+5=20\text{m/s} \\ {E}_2=\frac{1}{2}\cdot m\cdot v_2^2=\frac{1}{2}\cdot 80\cdot 20^2=16000\text{J} \end{gathered}$$

$$\begin{gathered} v_3=r_1-r_2=15-5=10\text{m/s} \\ {E}_3=\frac{1}{2}\cdot m\cdot v_3^2=\frac{1}{2}\cdot 80\cdot 10^2=4000\text{J} \end{gathered}$$

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