In this chapter, students will learn to define key concepts such as momentum, force, inertia, friction, and centripetal force. They will solve problems related to the relationship between force and momentum and illustrate the concept of force with practical examples from daily life. Additionally, students will state Newton’s laws of motion and differentiate between mass and weight, solving related problems. They will also calculate tension and acceleration in a string when bodies are connected and passing over a frictionless pulley. The chapter will cover the law of conservation of momentum and its application in analyzing the collision of two objects, enabling students to determine the velocity after a collision. Furthermore, they will explore how friction affects vehicle motion, considering tire surface and road conditions, including skidding and braking force. Lastly, students will demonstrate that rolling friction is significantly less than sliding friction and will list various methods to reduce friction.

FORCE, INERTIA AND MOMENTUM

Newton’s laws of motion are essential for understanding the causes of a body’s motion, and before delving into these laws, it’s important to grasp key concepts such as force, inertia, and momentum. Force is the influence that can cause an object to move, change its direction, or come to a stop. For instance, when we push or pull an object, such as a door or a cart, we apply force that can either initiate movement, alter its trajectory, or halt its motion altogether. However, force does not always result in movement; for example, when someone pushes against a wall, they exert force without moving it. Additionally, a goalkeeper requires force to stop a ball coming toward them. Overall, force plays a crucial role in initiating, stopping, or changing the direction of motion in various scenarios.

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NEWTON’S FIRST LAW OF MOTION

Newton’s first law of motion explains how objects behave when no forces are acting on them. It states that an object at rest will stay at rest unless something pushes or pulls it. For example, a book on a table won’t move unless someone lifts it. Similarly, an object in motion will keep moving in a straight line at the same speed unless a force stops it. For instance, a ball rolling on a rough surface will stop sooner than one on a smooth surface because the rough surface creates more friction. In short, the law says that an object will either stay still or keep moving in a straight line if no net force is acting on it.

NEWTON’S SECOND LAW OF MOTION

Newton’s second law of motion explains what happens when a net force is applied to an object. It states that when a force acts on an object, it causes the object to accelerate in the direction of that force. The amount of acceleration depends on two things: the size of the force and the mass of the object. Specifically, the stronger the force, the greater the acceleration, while a heavier object will accelerate less than a lighter one when the same force is applied. In simple terms, more force means more acceleration, but heavier objects require more force to achieve the same acceleration.