Kimberly Williams (13867793)
Physics
Wednesday, June 26, 2013
Unit 2 Assignment 1: Newton’s Laws (Portfolio) * Describe force as it applies to linear motion. * Motion that takes place along a straight line. Mechanical energy can take the form of rotary or linear motion. The push or pull that gives energy to an object. A force changes an object's motion or state of rest. * Explain what is meant by a net or unbalanced force. * An unbalance force is one that is not opposed by an equal and opposite force operating directly against the force intended to cause a change in the object's state of motion or rest. * Explains Newton’s first law of motion. * Newton's first law states that every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force. This is normally taken as the definition of inertia. The key point here is that if there is no net force acting on an object then the object will maintain a constant velocity. If that velocity is zero, then the object remains at rest. If an external force is applied, the velocity will change because of the force. * Explains Newton’s second law of motion. * The acceleration of a body is directly proportional to, and in the same direction as, the net force acting on the body, and inversely proportional to its mass. Thus, F = ma, where F is the net force acting on the object, m is the mass of the object and a is the acceleration of the object. * Apply Newton’s second law of motion to physical situations. * Returning to the baseball example, when the bat makes contact with the ball, the bat is exerting force on the ball. To determine the amount of that force, we multiply the mass of the bat, by the speed of the bat as it hits the ball. The weight of the bat is 822 g. When the bat hits the ball, the bat is traveling at about 20 meters per second. Therefore, by multiplying 822 g by 20 meters per second, we can determine that the bat exerts 16,440 newtons (N) of force on the baseball. That, along with other factors like ball weight and size, help determine how far the baseball will go. * Distinguish between weight and mass. * Mass is a measure of how much matter an object has. Weight is a measure of how strongly gravity pulls on that matter. Thus if you were to travel to the moon your weight would change because the pull of gravity is weaker there than on Earth but, your mass would stay the same because you are still made up of the same amount of matter. * Explain Newton’s third law of motion. * When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction to that of the first body. * Identify action-reaction force pairs. * An action-reaction pair is a pair of objects that interact to produce a force on each other of equal magnitude but of opposite direction. Object A exerts a force on object B that pushes/pulls it; and object B exerts a force on object A that pulls/pushes it. * Use Newton’s second law to determine forces acting on an object and the
