- #1
Nelonski
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Homework Statement
1) A 1000-kg Car is parked on a 10 degree slope. Determine the magnitude of the frictional force acting on the car
2) A 2000-kg car traveling at an initial speed of 10m/s skids to a stop with a constant acceleration. The coefficient of friction between the tired and the road is 0.4. determine the length of the skid marks
Homework Equations
Newtons 2nd law f=ma
(f_s) = static friction
f_k= kinetic friction
w= weight
n= normal force
The Attempt at a Solution
For the first part (1) . The free body diagram I drew was on a slant to show that the normal force is perpendicular to the slanted road so it is in the positive y direction, the force of static friction is to the negative x axis, and the weight force is downwards (with two components x and y)
F_x = -f_s + wsin∅ = 0
F_y= n-wcos∅=0
Essentially, I just solved the x component equation, given that wsin∅ is 9800sin10.
This was then equal to the static friction force.
This feels wrong, it was too simple, but maybe I could just be overthinking/underthinking.
Is this correct?
2)The normal force is pointing up in the positive y axis, the weight force is pointing down, and the kinetic friction force is poiting to the negative x axis(left) for the free body diagram.
Equations:
F_x= -f_k=ma_x
F_y= n-w=0
I esentially solved for the normal force in the y direction, then plugged that into f_k=μkn , to solve for the kinetic friction force. after solving the friction, I plugged that into F_x and determined the acceleration (which is negative).
After knowing the acceleration, initial and final velocities I used the equation
v_f^2=v_i^2+2aΔx
Solved for x, and think i found the answer.
Is this right as well? (the mah is entirely tough to type out so I simply gave my steps for solving)
Thanks so much