NCERT Solutions Class 9 Science Chapter 9 - Force and Laws of Motion

Why do the speeds of objects change with time? Do all motions require causes, and, if so, what is the nature of those causes? In Force and Laws of Motion Class 9, we discuss how the nature of force explains these types of questions. For example, force can increase or decrease the speed of an object, or change its direction of motion. Moreover, force can change the shape and size of objects. The mechanisms and general considerations that follow will be addressed in force and laws of motion class 9 solutions. 

The solutions to Class 9 Science Chapter 9 Exercise Solutions provide a comprehensive and clear understanding of force, types of forces, and Newton's three laws of motion. These solutions are prepared by India's premier subject-matter experts from ALLEN, who have helped thousands of students and are aimed to make it easier for students to understand the fundamental concepts. 

Through doing NCERT Solutions for Class 9 Science Chapter 9 exercise questions, students can successfully practice and build their understanding of the chapter. The solutions are useful to gauge where you are in your understanding of the concepts and merits of the chapter? More importantly, they are a great material for quick revision before exams as they cover each topic throughout all exercises and exam questions often come directly from these exercises.

1.0What Will Students Learn in Chapter 9: Force and Laws of Motion?

• An object will remain in its state of rest or uniform motion in a straight line unless acted upon by an unbalanced force. This natural ability of objects to resist change in their state of rest or motion, is called inertia. The mass of an object is a measure of its inertia, where the SI unit is kilograms (kg).
• Frictional forces oppose the motion of objects.
• The second law of motion states that the rate of change of momentum of an object is proportional to the applied unbalanced force in the direction applied. 
• The SI unit for force is kg m s-2, referred to as Newtons, and given the symbol N.  One Newton of force would provide an acceleration of 1 m s-2 and act on an object of mass 1 kg. 
• The momentum of an object is the product of its mass and velocity, and has the same units (and direction) as velocity. The SI unit for momentum is kg m s-1. 
• The third law of motion states that for every action there is an equal and opposite reaction, however these two forces act on different bodies. 
• In an isolated system, where there is no external force, the total momentum remains constant.