In the first part we saw that Force is not just a human pushing or pulling an object. Force is a push or pull upon an object resulting from its interaction with another object. There are two things we will cover in this video : Types of forces and the effects of forces For simplicity we can classify forces into two types Contact forces and Non-contact forces. Contact forces are just what they sound like Forces that result from the interaction of two objects in contact with each other. Are there any contact forces that you know of? Of course you know a few! What happens when you softly kick the ball which is lying on the ground? You apply the force on the ball, and there was contact. Applied Force is one of the contact forces. Next there is a force of friction which brings the ball to a halt. As the ball is in contact with the ground, frictional force is also a contact force. Don’t you think there was some air resistance? Yes! Air resistance too is a contact force. The normal force which is applied force in the upward direction is a contact force as well These were some of the contact forces we know of but these are not the only ones. Can you think of any non-contact force? What happens when the ball is in the air? It will fall down, right? What pulls the ball down? Yes, it’s the gravitational pull which is trying to pull the ball towards the center of the earth. This pull happens even if the object is not in physical contact with the earth. The gravitational force is an example of a non-contact force. Other examples of non-contact forces are electrical and magnetic forces. Now i want you to think about the next question i’m going to ask you. What all can a force do? What can be its effects? Let me give an example. Force can set a stationary object in motion. That’s one of the things force can do. Can you think of the other things it can do? Assume an object is moving at a uniform velocity of two meters per second. If it is pushed harder its velocity will increase. So force can also change the velocity of an object. Force can also stop a moving object. Anything else you can think of? Yes, force can also change the direction of a moving object. If a ball is moving towards the north, a kid from the right can change its direction to north-west. Is there anything else you can think of force can do? Come on! I want you to think really hard. Don’t think only in terms of motion. Force can also change the shape of an object. If we apply force from both sides to a spherical ball, its shape changes. The ball’s position does not change, but its shape does. So these are some of the things that force can do. In the next video we will play an interesting game to know if you really understood how forces act on an object.