Which of the following is the best example of Newton's first law of motion? A. Whenever you push against a wall, the wall pushes back. B. When a bat hits a ball, the ball hits the bat. C. A rider on a running horse is thrown forward when the horse stops suddenly. D. A 100-g baseball will accelerate more slowly than a \(50-\mathrm{g}\) baseball because of its greater mass.

Newton's First Law of Motion, also known as the law of inertia, states that an object will remain at rest or in uniform motion unless acted upon by an external force. This means if you leave something alone, it won't change its state by itself. For example, if a ball is sitting on the ground, it won't start rolling unless you push it. Similarly, if the ball is rolling, it won't stop unless a force, like friction, slows it down.
The law of inertia explains why you feel a jolt forward when a car stops suddenly. Your body wants to keep moving forward because there is no force stopping your motion until the seatbelt or dashboard intervenes.

Newton's Second Law of Motion establishes the relationship between force, mass, and acceleration. It states that the force acting on an object is equal to the mass of that object multiplied by its acceleration. The equation is given by:


This law explains why lighter objects accelerate more quickly under the same force. For example, pushing a light ball will make it roll faster than pushing a heavier ball with the same force.
Understanding Newton's second law helps us explain everyday activities, such as why it's harder to push a full shopping cart compared to an empty one.

Newton's Third Law of Motion is all about action and reaction. It states that for every action, there is an equal and opposite reaction. This means that forces always come in pairs. If you push on a wall, the wall pushes back with the same force in the opposite direction.
Examples of Newton's third law are everywhere. Think about swimming: when you push water backward with your hands, the water pushes you forward. The same principle applies when a bird flies; its wings push air downwards, and in response, the air pushes the bird upwards.

The interplay of forces and motion is central to understanding the principles of mechanics. Forces can make objects start moving, stop moving, or change direction. A force is essentially a push or a pull acting on an object.
There are different types of forces, including gravitational force, frictional force, and applied force. Gravitational force is what keeps us grounded on Earth. Frictional force opposes motion, like when brakes are applied to a bicycle. Applied forces are those that you manually exert, like pushing a swing.
In summary, forces affect how objects move and interact. Mastering the concepts of forces and motion helps explain and predict how objects behave in the real world.