# The work of the traction force of a car that has passed with an unchanging universe, in essence

The work of the traction force of a car that has passed with an unchanging universe, in essence, a path of 2 km is equal to 50 kJ, determine the force of friction.

We translate the values ​​from given to the SI system:
S = 2 km = 2000 m.
A = 50 kJ = 50,000 J.
According to Newton’s second law:
The acceleration acquired by the body as a result of the impact on it is directly proportional to the strength of this impact and inversely proportional to the body mass:
F = m * a
In our case, the following forces act on the body:
Ft + Fc = ma, Ft – traction force, Fc – drag force (friction force).
Let’s write in projections on the axis, taking into account that the body moves uniformly:
ОУ: Fт + Fc = 0
Fт = Fc
The work is equal to the pulling force multiplied by the displacement:
A = Fт * S
Let us express Ft from this expression and substitute it into Newton’s second law:
Fт = A / S
Fc = Fт = A / S
Substitute the numbers and determine the friction force:
Fc = A / S = 50000/2000 = 25 N.
Answer: the friction force is 25 N.

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