Class 11

NCERT Solutions for Chapter 9 Straight Lines are expert-prepared explainations to all textbook questions. These Solutions are designed to help Class 11 students understand concepts like slope, line equations, angles between lines, and more. These solutions simplify complex problems through step-by-step explanations, making it easier to grasp coordinate geometry. Perfect for exam preparation, they follow the latest CBSE syllabus and are useful for both board exams and competitive exams like JEE. Whether you're revising or stuck on a tricky question, these solutions offer clear guidance. They're also available in free downloadable PDF format, so you can study offline anytime.

Mass measures the amount of matter an object contains and it is a fundamental property of an object. It remains constant irrespective of the object's location, it is a scalar quantity. The SI unit of mass is the kilogram (kg). On the other hand, weight is a vector quantity and refers to the force exerted on an object due to gravity. The SI unit of weight is the Newton (N).Mathematically, the relation between mass and weight is given by W=mg, W=weight, m= mass, and g=acceleration due to gravity. The g's value varies based on the location. Therefore, while the mass of an object remains constant, the weight can change depending on the gravitational field.

According to Newton's third law of motion, every action has an equal and opposite reaction. These action-reaction forces act on different objects. The real-world example is a person walking, when the person takes a step forward, their foot pushes backward on the ground, the ground also exerts an equal and opposite force forward on the person's foot and the person is propelled forward due to the reaction force from the ground. Another real-world example is the rocket launch which expels hot gases downward (action), the gases exert an equal and opposite upward force (reaction) on the rocket and cause upward acceleration. It is an important point to remember that the action and reaction forces act on different bodies and hence although they are equal and opposite, they do not cancel each other out.

Newton's First Law of Motion is also known as the Law of Inertia. It states that unless acted upon by an unbalanced force, the object in motion stays in motion in the same direction and with the same speed and the object at rest stays at rest. The fundamental concept of inertia is introduced by the first law of Newton which refers to the resistance an object shows to changes in its state of motion. It is an inherent tendency of an object. Inertia is directly proportional to an object's mass which implies that a massive object has greater inertia and will require more force for velocity changes.

Newton's First Law of Motion implies that to cause acceleration i.e. velocity changes, a net force is needed and in the absence of the net force, the objects maintain their current state of motion. This law challenges the earlier Aristotelian view which stated that to keep an object moving, a continuous force is required.