# The bus, the mass of which is 15 tons, starts to move with an acceleration of 0.7 m / s2

**The bus, the mass of which is 15 tons, starts to move with an acceleration of 0.7 m / s2. Find the force of resistance to movement if the traction force is 15 kN**

m = 15 t = 15000 kg.

V0 = 0 m / s.

a = 0.7 m / s2.

Ft = 15 kN = 15000 N.

Fsopr -?

According to 2 Newton’s law, the product of the mass of the bus m by its acceleration is equal to the resultant of all forces Fр that act on the bus: m * a = Fр.

The resultant of all forces Fр is called the vector sum of all forces that act on the bus. In the direction of travel, a traction force Ft acts on the bus, and a resistance force Fcopr acts in the opposite direction of the direction of travel. The resultant Fr is expressed by the difference: Fr = Ft – Fcopr.

m * a = Fт – Fc.

Fcopr = Ft – m * a.

Fcopr = 15000 N – 15000 kg * 0.7 m / s2 = 4500 N.

Answer: when driving on the bus, the resistance force Fcopr = 4500 N.