1. The problem statement, all variables and given/known data A car moving at 50mph coasts to a stop while travelling a distance of 150ft on level ground. what is the size of the friction force needed to bring this car to rest? 2. Relevant equations vf^2 = vo^2 + 2a(xf-xo) F=ma Fk=un 3. The attempt at a solution I first converted everything to meters and seconds. So, initial velocity is 22.35 m/s and distance travelled is 47.7 meters. Then, I found acceleration, which is -5.24 m/ss. Then, I found time. 4.27 seconds I tired to find the coefficient of friction with: F=ma=u(mg) (n is the same as mg because the surface is level) ma=u(mg) a=ug -5.24=u(-9.8) u=0.53 I have no idea what to do now. It wants the friction force, not the coefficient. those are pretty much the only formulas we have at this point. We haven't gotten to work or energy formulas.