Transcript Chapter 3
Chapter 3 Forces Newton’s Second Law • Forces and motion are connected – An object will have greater acceleration if a greater force is applied to it. – The mass of an object and the force applied to it affect acceleration. Newton’s Second Law • Acceleration equals net force divided by mass. • Friction- force that opposes motion between two surfaces that are touching each other. F=ma Newton’s Second Law – microwelds, areas where surface bumpers stick together, are the source of friction. – Static friction=two surfaces not moving past each other – Sliding friction= opposes the motion of 2 surfaces sliding past each other – Rolling friction=between the rolling object and the surface it rolls on (tire on pavement) Newton’s Second Law • Air Resistance-opposes force of gravity upward force exerted on an object falling through air-explains why a brick falls faster than a feather – amount depends on object’s shape, size and speed – terminal velocity- forces on a falling object are balanced and the object falls with constant speed Gravity • Law of Gravitation-any two masses exert an attractive force on each other. Amount of gravitation force between objects depends on their masses and the distance between them. – One of the 4 basic forces that also include the electromagnetic force, the strong nuclear force, and the weak nuclear force. – Long range force that gives the universe its structure Gravity • Due to inertia, all objects fall with the same acceleration regardless of mass. An object that is in free fall seems to be weightless Gravity • Weight – decreases as an object moves away from Earth. – weight results from a force; mass is a measure of how much matter an object contains weight=measure of the force of gravity on an object N mass=measure of the amount of matter in an object g and kg Gravity • Objects in the space shuttle float because they have no force supporting them. Gravity parallel to Earth’s surface • Projectiles have horizontal and vertical velocities due to gravity, and follow a curved path. Circle Gravity • Acceleration toward the center of a curved path is called centripetal acceleration; it is caused by centripetal force, an unbalanced force. (car rounding a curve) – satellites are anything that moves around another body in a generally circular path. moon=natural satellite space station=artificial satellite The Third Law of Motion • To every action force there is an equal and opposite reaction force. – action-reaction forces act on different objects and differ from balanced forces – example= rocket propulsion action force up=reaction force down action force right=reaction force left The Third Law of Motion • Momentum-related to how much force is needed to change an object’s motion. momentum=mass times velocity p=mv kg X m/s p=momentum The Third Law of Motion • Law of conservation of momentummomentum can be transferred between objects; momentum is not lost or gained in the transfer When two objects collide…