Define following forces with one example …

1. Frictional Force- Friction is a force that comes into play when two surfaces comes in contact with each other. The frictional force or the force of friction acts in the opposite direction of the motion of the object. The force of friction opposes the relative motion between the surfaces of two moving objects. For example- if a book slides across the surface of the desk, then the desk exerts a frictional force in the opposite direction of the friction. 2. Gravitational force- The gravitational force is a force that attracts any two objects with mass. We call the gravitational force attractive because it always try to pull masses together, it never pushes them apart. In fact, every object, including you , is pulling on every other object in the entire universe! For Example- the force that when you throw the ball up in the sky, it again comes down to the ground.

Frictional Force is a force that acts on all moving objects by the surface which it is in contact with. Eg: A ball rolling on the ground encounters friction by the ground surface and it eventually comes to a halt. When the rowing of the boat has stopped, the boat comes to a stop because of the frictional force exerted by water on it. The Frictional force is always in the direction opposite to the applied force.

Gravitational force is a force exerted by the earth on all objects on it. When a ball is thrown up, it falls to the ground because of gravitational force. The water from a tap always flows downwards because of gravitational force.