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

chroncile

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

Fapp = 151 N
Fn = 156 N

How would you get the normal force?

Related Introductory Physics Homework News on Phys.org

PhanthomJay

Homework Helper
Gold Member
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

Fapp = 151 N
Fn = 156 N

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

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving