9 (d) First Law of Motion
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Newton’s first law of motion is also called the law of inertia. Inertia explains why you move forward in
your seat when a car stops suddenly. When the car stops, inertia keeps
you moving forward.
Newton’s first law of motion states that an object at rest will remain at rest, and an object moving at a constant velocity will continue moving at a constant velocity, unless it is acted upon by an unbalanced force. If an object is not moving, it will not move until a force acts on it. Clothes on the floor of your room, for example, will stay there unless you pick them up. If an object is already moving, it will continue to move at a constant velocity until a force acts to change either its speed or direction. For example, a tennis ball flies through the air once you hit it with a racket. If your friend doesn’t hit the ball back, the forces of gravity and friction will eventually stop the ball. On Earth, gravity and friction are unbalanced forces that often change an object’s motion.
Inertia
Whether an object is moving or not, it resists any change to its motion. The resistance to a change in motion is called inertia. Inertia (in ur shuh) is the tendency of an object to resist a change in motion. Newton’s first law of motion is also called the law of inertia.
Inertia explains many common events, such as why you move forward in your seat when a car stops suddenly. When the car stops, inertia keeps you moving forward. A force, such as the pull of a seat belt, is required to change your motion.
Inertia Depends on Mass
Some objects have more inertia than other objects. For example, suppose you needed to move an empty aquarium and an aquarium full of water. Obviously, the full aquarium is harder to move than the empty one, because it has more mass. The greater the mass of an object is, the greater its inertia, and the greater the force required to change its motion. The full aquarium is more difficult to move because it has more inertia than the empty aquarium.
Newton’s first law of motion states that an object at rest will remain at rest, and an object moving at a constant velocity will continue moving at a constant velocity, unless it is acted upon by an unbalanced force. If an object is not moving, it will not move until a force acts on it. Clothes on the floor of your room, for example, will stay there unless you pick them up. If an object is already moving, it will continue to move at a constant velocity until a force acts to change either its speed or direction. For example, a tennis ball flies through the air once you hit it with a racket. If your friend doesn’t hit the ball back, the forces of gravity and friction will eventually stop the ball. On Earth, gravity and friction are unbalanced forces that often change an object’s motion.
Inertia
Whether an object is moving or not, it resists any change to its motion. The resistance to a change in motion is called inertia. Inertia (in ur shuh) is the tendency of an object to resist a change in motion. Newton’s first law of motion is also called the law of inertia.
Inertia explains many common events, such as why you move forward in your seat when a car stops suddenly. When the car stops, inertia keeps you moving forward. A force, such as the pull of a seat belt, is required to change your motion.
Inertia Depends on Mass
Some objects have more inertia than other objects. For example, suppose you needed to move an empty aquarium and an aquarium full of water. Obviously, the full aquarium is harder to move than the empty one, because it has more mass. The greater the mass of an object is, the greater its inertia, and the greater the force required to change its motion. The full aquarium is more difficult to move because it has more inertia than the empty aquarium.
