quick physics questions?

[pimpdaddy5822]

1. A 15.0 kg box is released on a 39.0° incline and accelerates down the incline at 0.269 m/s2. The friction force impeding its motion is 88.5. What is the coefficient of kinetic friction?
_______

2. An elevator in a tall building is allowed to reach a maximum speed of 3.6 m/s going down. What must the tension be in the cable to stop this elevator over a distance of 3.2 m if the elevator has a mass of 1280 kg including occupants?
_____N


3. Police lieutenants, examining the scene of an accident involving two cars, measure the skid marks of one of the cars, which nearly came to a stop before colliding, to be 81 m long. The coefficient of kinetic friction between rubber and the pavement is about 0.60. Estimate the initial speed of that car assuming a level road.
_____m/s