Question

A clay ball with a mass of 0.35 kg has an initial speed of 4.2 m/s. It strikes a 3.5 kg clay ball at rest, and the two balls stick together and remain stationary. What is the decrease in kinetic energy of the 0.35 kg ball?

Answer 1

$\begin{gathered} m=0.35\text{ kg} \\ v1=4.2\text{ m/s} \\ v2=0\text{ m/s} \\ K1=\frac{mv1^2}{2} \\ K1=\frac{\left(0.35kg\right)\left(4.2m/s\right)^2}{2} \\ K1=3.087J \\ K2=\frac{mv2^2}{2} \\ K2=\frac{\left(0.35kg\right)\lparen0\text{ m/s\rparen}^2}{2} \\ K2=0\text{ J} \\ Decrease=K1-K2 \\ Decrease=3.087J-0\text{ J} \\ Decrease=3.087J \\ The\text{ decrease in kinetic energy is 3.087 J} \end{gathered}$