Effect of force: 

1.Force change the motion of a body:- force change the motion of body that are already in motion and produce motion in a stationary body. Example a car moving on a road suddenly hit behind by a truck, you will notice the tendency of the car motion increase. the force applied by the truck affect the motion of the car. A stationary body hit behind by a moving body, the position of the stationary body changes. 

2.Force change the direction of both stationary body and body in motion:-Newston second law state that the rate of change of momentum of a body is directly proportional to the applied force and take place in the direction in which the force acts. 

3.Frictional force:- is a force that oppose the motion of one body over the other. 
Effect of frictional force: 
a.It leads to wasting of energy, when two surrounding forces move over each other, heat is generated as a resultof friction. the energy required to turn the machine, will be converted heat energy which reduces the energy output. 
b.It leads to wearing away of the surfaces in contact. 

4.Gravitational force field:- Gravitational force field couse body thrown up to fall back on the ground.