Newton's Laws Finding Applied Force and other Forces

[jackilynn]

1. Sean the skier is headed for a rough patch of snow with the coeffcient of friction 0.20. Find his acceleration if his mass is 50 kg.
2. F=ma, coeffcient of friction=Ff/Fn
3. Fgravity = 490.5 using the equation coeffcient of friction=Ff/Fn we get 0.20 = Ff/490.5 which equals Ff = 98.1
This is where i get stuck. i do not know how to find the Force applied to use it to find the sum of the two forces (force applied and force of friction) to plug into the equation F= ma.

 

[dikmikkel]

The sum of forces equals ma (Newtons 2nd law). Use it to write down the equation(s) to be solved.
You know that the vertical acceleation is zero:
$0= N - mg\\<br /> F_{fric} = \mu N=\mu mg\\<br /> \sum F_{horizontal} = ma = -F_{fric}$
So never plug into any equation unless you have a good reason