Answer:
A force of 83 N is needed to pull the sled with constant speed.
Explanation:
Hi there!
Please, see the attached figure for a graphical description of the problem.
We have the following horizontal forces applied on the sled:
F = applied force.
Fr = friction force.
And the following vertical forces:
N = normal force.
W = weight of the sled + weight of the person
According to the Newton´s second law:
∑F = m · a
Where "m" is the mass of the object and "a" is its acceleration
So, in the horizontal direction:
F - Fr = m · a
We have to find what force, F, is needed so that the sled moves with constant speed (acceleration = 0). Then:
F - Fr = 0
F = Fr
The applied force has to be equal in magnitude to the friction force.
The friction force is calculated as follows:
Fr = μ · N
Where μ is the coefficient of friction and N is the normal force.
To find the normal force, let´s apply Newton´s second law in the vertical direction:
∑F = N - W = m · a
Notice that the sled is not accelerated in the vertical direction so that a = 0:
N - W = 0
N = W
The normal force is equal to the weight and the weight is the sum of the weight of the sled plus the weight of the person:
W = 52 N + 700 N = 752 N
Then:
N = 752 N
Fr = 0.11 · 752 N
Fr = 83 N
Then
F = 83 N
A force of 83 N is needed to pull the sled with constant speed.
A force of 83 N is needed to pull the sled with constant speed.
We have the following horizontal forces applied on the sled:
F = applied force.
Fr = friction force.
And the following vertical forces:
N = normal force.
W = weight of the sled + weight of the person
According to the Newton´s second law:
F = m * a
Where "m" is the mass of the object and "a" is its acceleration
So, in the horizontal direction:
F - Fr = m *a
To find what force, F, is needed so that the sled moves with constant speed (acceleration = 0). Then,
F - Fr = 0
F = Fr
The applied force has to be equal in magnitude to the friction force.
The friction force is calculated as follows:
Fr = μ · N
Where μ is the coefficient of friction and N is the normal force.
To find the normal force, let´s apply Newton´s second law in the vertical direction:
F = N - W = m · a
Notice that the sled is not accelerated in the vertical direction so that a = 0:
N - W = 0
N = W
The normal force is equal to the weight and the weight is the sum of the weight of the sled plus the weight of the person:
W = 52 N + 700 N = 752 N
Then:
N = 752 N
Fr = 0.11 · 752 N
Fr = 83 N
Then
F = 83 N
A force of 83 N is needed to pull the sled with constant speed.
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