NCERT Solutions for Class 9 Science Unit 9
Force and Laws of Motion Class 9
Unit 9 Force and Laws of Motion Exercise Solutions
It is the force that enables us to do any work. To do anything, either we pull or push the object. Therefore, pull or push is called force.
Example - to open a door, either we push or pull it. A drawer is pulled to open and pushed to close.
Galileo Galilei: Galileo first of all said that object move with a constant speed when no forces act on them. This means if an object is moving on a frictionless path and no other force is acting upon it, the object would be moving forever. That is there is no unbalanced force working on the object. But practically it is not possible for any object. Because to attain the condition of zero unbalanced force is impossible. Force of friction, force air and many other forces always acting upon an object.