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Newton's 2nd Law Question (2-Dimensions)

  • Thread starter chroncile
  • Start date
1. The problem statement, all variables and given/known data
A proud homeowner is out mowing their lawn. If the force of friction on the mower is 50.0 N and it is accelerating forward at 0.15 m/s2, what is the magnitude of the applied force if the owner is pushing on the handle of the mower at an angle of 70 below the horizontal? How big is the normal force acting on the lawnmower? The mass of the lawnmower is 11 kg.


2. Relevant equations
Fnet = Fapp + Ff
Fnet = ma
Fg = mg

3. The attempt at a solution
Fnet = Fapp + Ff
0.15 * 11 = Fappx + (-50.0)
1.65 + 50.0 = Fappx
Fappx = 51.65 N

Fappy = 51.65 * tan(70) = 142 N

Fapp = SquareRoot (51.652 + 1422)
Fapp = 151 N

0 = Fappy + Fn + Fg
0 = 142 + Fn + 11*9.8
Fn = -250 N

Correct answers are:

Fapp = 151 N
Fn = 156 N

How would you get the normal force?
 

PhanthomJay

Science Advisor
Homework Helper
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1. The problem statement, all variables and given/known data
A proud homeowner is out mowing their lawn. If the force of friction on the mower is 50.0 N and it is accelerating forward at 0.15 m/s2, what is the magnitude of the applied force if the owner is pushing on the handle of the mower at an angle of 70 below the horizontal? How big is the normal force acting on the lawnmower? The mass of the lawnmower is 11 kg.


2. Relevant equations
Fnet = Fapp + Ff
Fnet = ma
Fg = mg

3. The attempt at a solution
Fnet = Fapp + Ff
0.15 * 11 = Fappx + (-50.0)
1.65 + 50.0 = Fappx
Fappx = 51.65 N

Fappy = 51.65 * tan(70) = 142 N

Fapp = SquareRoot (51.652 + 1422)
Fapp = 151 N

0 = Fappy + Fn + Fg
0 = 142 + Fn + 11*9.8
Fn = -250 N

Correct answers are:

Fapp = 151 N
Fn = 156 N

How would you get the normal force?
Your way:smile:. There seems to be an error in the problem solution.
 

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