Report

Momentum Notes Sports Momentum The sports announcer says "Going into the all-star break, the San Diego Padres have the momentum." The headlines declare "Chargers Gaining Momentum." The coach pumps up his team at half-time, saying "You have the momentum; the critical need is that you use that momentum and bury them in this third quarter." A team that has the momentum is on the move and is going to take some effort to stop. Physics Momentum Momentum can be defined as "mass in motion.“ All objects have mass, so if an object is moving, then it has momentum - it has its mass in motion. Momentum = mass • velocity In physics, the symbol for the quantity momentum is the lower case "p". Thus, the above equation can be rewritten as p=m•v Momentum Units The units for momentum would be mass units times velocity units. The standard metric unit of momentum is the kg•m/s. Momentum Vectors Momentum is a vector quantity, which is fully described by both magnitude and direction. The direction of the momentum vector is the same as the direction of the velocity of the ball. Practice Determine the Momentum of a. 60-kg halfback moving eastward at 9 m/s. p = m*v = 60 kg*9 m/s p = 540 kg•m/s, east b. 1000-kg car moving northward at 20 m/s. p = m*v = 1000 kg*20 m/s p = 20 000 kg•m/s, north c. 40-kg freshman moving southward at 2 m/s p = m*v = 40 kg*2 m/s p = 80 kg•m/s, south More Practice A car possesses 20,000 units of momentum. What would be the car's new momentum if ... a. its velocity were doubled. b. its velocity were tripled. c. its mass were doubled (by adding more passengers and a greater load) d. both its velocity were doubled and its mass were doubled. Answers a. p = 40,000 units (doubling the velocity will double the momentum) b. p = 60,000 units (tripling the velocity will triple the momentum) c. p = 40,000 units (doubling the mass will double the momentum) d. p = 80,000 units (doubling the velocity will double the momentum and doubling the mass will also double the momentum; the combined result is that the momentum is doubled twice -quadrupled)