Solving Physics Homework: Frictional Force & Speed of Baseball Player

[jess_08]

Homework Statement

A baseball player of mass 80.0 kg slides into home base. The coefficient of kinetic friction between the player and the ground is 0.610.
a.) What is the magnitude of the frictional force? (In solving this part of the question draw a free body diagram with all of the forces labelled. Use a rectangle to represent the baseball player. Also, assume the player is moving to the right while sliding.)
b.) If the player comes to rest after 1.5 s, what must have been the initial speed of the player?

Homework Equations

The Attempt at a Solution

 

[learningphysics]

can you show your work? where are you getting stuck?

 

[jess_08]

i don't even know where to start... like what do i do?

 

[noyaz]

Fn
|
<-- Ff (0.610)RECTANGLE(80.0kg)----> Fa(his sliding)
|
Fg

Fk=mue Fn
Fk=(0.610)mg
Fk=(0.610)(80)(9.81)
=478.725N

ahha i honestly made up that answer for part a... but the FBD is right (:

 

[jess_08]

k i understand that equation but how do i find the average force to find the acceleration in part b?