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Newton’s Second Law. Physical Science 3.1. Force and Acceleration. Greater force = greater acceleration Applying force causes change in velocity Velocity change over a shorter period of time = more acceleration change Same force on different object may result in different acceleration
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Newton’s Second Law Physical Science 3.1
Force and Acceleration • Greater force = greater acceleration • Applying force causes change in velocity • Velocity change over a shorter period of time = more acceleration change • Same force on different object may result in different acceleration • More mass = less acceleration • Newton’s 2nd law: The net force acting on an object causes the object to accelerate in the direction of the net force • a = F/m
Force and Acceleration • Units • Mass: kg • Acceleration: m/s2 • Force: N = kg*m/s2 • a = F/m also written as F = ma • Friction: The force that opposes motion between two surfaces that are touching each other • 2 Factors influencing amount of friction • Kinds of surfaces and the force pressing the surfaces together
Friction • Surfaces of objects are rough microscopically • Cause of friction: microwelds- when highest bumps from each surface stick together • Stronger forces pushing surfaces together = stronger microwelds • Static friction: - the friction between two surfaces that are not moving past each other
Friction • Sliding friction- the reason you must continue to apply force after starting motion • Acts against your push • Microwelds constantly break and reform • Lack of friction = lack of motion for us and vehicles • Rolling friction- Friction between rolling object and surface- due to microwelds between wheel and surface it rolls over • Weakest form of friction
Air Resistance • On earth- feather falls slower than tennis ball due to air resistance • Air resistance- force acting opposite to motion of falling object • Depends on Speed, size, and shape of falling object • In vacuum (no air) - feather and tennis ball fall at the same rate- no air resistance • Terminal velocity- highest velocity a falling object can reach • When the forces on a falling object are balanced