Galileo and Newton's Laws of Motion

Inertia and State of Motion

• Galileo Galilei described the concept of inertia, which is the tendency of objects to stay at rest or in motion.
• Newton's first law, the law of inertia, states that an object in a state of uniform motion tends to remain in that state of motion unless acted on by an outside force.
• State of motion refers to how an object is moving (or not moving), and can be described in various ways, such as slowly, fast, in circles, or in a straight line.

Speed and Distance

• Galileo was the first to measure speed, which is the distance an object covers in a given amount of time.
• Speed is a calculation of distance divided by time, and can be expressed in various units, such as kilometers per hour, meters per second, or centimeters per day.

Velocity and Direction

• Velocity is the combination of an object's speed and direction.
• Speed tells us how fast an object is going, while velocity tells us how fast and in which direction.
• An object can have a constant speed, but not a constant velocity, if it is changing direction, such as driving in a circle.

Constant Velocity and Inertia

• For an object's velocity to be constant, it must move in a straight line at the same speed.
• Inertia can be thought of as the tendency of an object to resist changes in velocity, rather than just motion.

Relative Motion

• Motion is relative, meaning it is described in relation to something else.
• An object can be considered at rest relative to one object, but in motion relative to another, such as a person sitting on a couch relative to the Earth, but moving relative to the sun.
• The velocity of an object can be described relative to different reference points, such as a car's velocity relative to the road, or a satellite's velocity relative to the Earth.