Two physics questions Help !?

Question

I have this two problem that I can't solve...

1) A baseball player slides into third base with an initial speed of 8.25 m/s. If the coefficient of kinetic friction between the player and the ground is 0.37, how far does the player slide before coming to rest?

___ m

How would i solve this when i only have the inital velocity and final and coefficient of kinetic friction?

2) Two crewmen pull a boat through a lock, as shown in Figure 5-25. One crewman pulls with a force of F1 = 155 N at an angle of θ = 36° relative to the forward direction of the raft. The second crewman, on the opposite side of the lock, pulls at an angle of 45°. With what force F2 should the second crewman pull so that the net force of the two crewmen is in the forward direction?

______N

In this problem, what am I solving for? Am I soloving for F2? If solve for that i get 177N.. and its wrong.. help plz T_T

Answer 1

1) The baseball player comes to a rest when the amount of work done on the player by the friction from the ground is equal to the amount of Kinetic energy that he had when he started his slide.

KE = 1/2 * m * v^2

Wf = mu * Fn * d

mu is the coefficient of friction and d is the distance.  Fn, since we are dealing with a non-inclined surface, is equal to the player's weight, or m*g.

Our equation for the work now looks like this:

Wf = mu * m *g * d

When we set that equal to the Kinetic Energy that the player had prior to sliding, we get:

mu * m * g * d = 1/2 * m * v^2

Notice that the mass of the player cancels out, so you can use the information that you have.

2) The goal in 2 is to find F2 such that the vertical components of the two forces cancel each other out.

F1 sin 36 = F2 sin 45

F1 sin 36 = 91.11

F2 = 91.11/sin 45

I get 129 N for F2.