# Homework Help: Horizontal motion problem involving coefficient of friction and initial velocity.

1. Oct 24, 2009

### chown

1. The problem statement, all variables and given/known data
A person slides to third base. The coefficient of kinetic friction between player and the ground is 0.70. His velocity at the start of the slide is 8.23m/s [forward].
Prove that the time it takes the player to come to a stop from sliding is:
time = initial velocity divided by (coefficient of kinetic friction X acceleration due to gravity)

acceleration due to gravity = 9.81 m/s^2 [down]
Mass = 80 kg
coefficient of kinetic friction = 0.70
initial velocity is 8.23 m/s [forward]

2. Relevant equations
Net force = mass times acceleration
coefficient of kinetic friction = force of friction/normal force
$$\Sigma F = net force$$

3. The attempt at a solution
The net force must be equal to the force of kinetic friction. Acceleration is therefore in the direction backwards. Without the mass given, I'm able to suggest equations as proof in a limited manner because the normal force, a necessary component in finding the force of friction, is proportional to the mass. How can I solve for time without the mass?

2. Oct 24, 2009

### Fightfish

Are you sure you need the mass? Try writing out the expression for the acceleration of the person due to the frictional force.

3. Oct 24, 2009

Thank you.