Question

A baseball player is running to second base at 6.94 m/s. When he is 5.10 m from the plate he goes into a slide. The coefficient of kinetic friction between the player and the ground is 0.15, and the coefficient of static friction is 0.23. What is his speed when he reaches the plate?

Answer 1

As the player starts sliding, its initial kinetic energy starts converting to work against friction, so, the final kinetic energy is smaller.

$$\frac12 mv^2=\mu_kmgx+\frac12mu^2,\\\space\\ u=\sqrt{v^2-2\mu_kgx},\\ u=\sqrt{6.94^2-2·0.15·9.8·5.1}=5.76\text{ m/s}.$$