NCERT Solutions for Class 9th Science Chapter 6 How Forces Affect Motion

About this chapter

A force has magnitude and direction . Its SI unit is the newton (N), measured with a spring balance. One newton is the force that gives a 1 kg object an acceleration of 1 m s –2 . Forces equal in magnitude and opposite in direction are balanced ; the net force is zero. Unbalanced forces give a non-zero net force — added when the forces point the same way, subtracted when they oppose. Motion depends only on the net force. Friction always acts opposite to the direction of motion (or attempted motion). It depends on the nature of the surfaces in contact. Without it, a moving object would never slow down on its own. Newton's first law: an object at rest stays at rest and an object in motion keeps moving with constant velocity unless a net force acts on it. Zero net force means zero acceleratio

• Chapter opener
• .2 Balanced and Unbalanced Forces
• .4 Newton's First Law of Motion
• .5 Newton's Second Law of Motion
• .6 Newton's Third Law of Motion
• .7 Forces Acting on a System of Objects
• End-of-chapter exercise
• Project work