A 10 kg rock, initially at rest, explodes into two fragments. A 4 kg fragment flies due East at 10 m/s. What is the velocity of the second fragment?

I NEED HELP ASAP

As a pendulum bob swings back and forth several times, the maximum height it reaches becomes less and less. this is because more and more of the pendulum bob's energy is being transformed into a. heat energy b. kinetic energy c. potential energy d. kinetic energy and potential energy