Linear motion, also known as rectilinear motion, is the movement of an object in a straight line. This can be in either a horizontal or vertical direction.
Newton's first law of motion, also known as the law of inertia, states that an object at rest will remain at rest and an object in motion will remain in motion at a constant velocity, unless acted upon by an external force.
Newton's second law of motion states that the force applied to an object is equal to the mass of the object multiplied by its acceleration. In the context of linear motion, this means that the acceleration of an object is directly proportional to the force applied and inversely proportional to the mass of the object.
Speed is a measure of how fast an object is moving, while velocity is a measure of how fast and in what direction an object is moving. In linear motion, both speed and velocity are measured in units of distance per unit of time (such as meters per second).
Friction is a force that opposes motion and acts in the opposite direction of an object's velocity. In linear motion, friction can slow down or even stop an object's movement if it is strong enough to counteract the applied force. It can also cause an object to change direction or experience a decrease in speed.