Section 1 review
Momentum is a vector quantity: the product of mass and velocity. Impulse (also a vector) is the change in an object’s momentum. Impulse can be expressed as the product of an applied force and the force’s duration. Cushioning increases the time interval for momentum transfer, and this reduces the forces felt in car crashes and contact sports. Read the text aloud
momentum, impulse

p =m v
J=Δp=FΔt

Review problems and questions

  1. State one similarity and one difference between inertia and momentum. Read the text aloud Show
  1. A hockey puck that has a mass of 170 g travels with a speed of 30 m/s.
    1. What is the momentum of the puck?
    2. What impulse must be imparted on the puck by a player who wishes to change the puck’s direction by 180°, while keeping the puck moving at the same speed? Read the text aloud Show
  1. Julieta kicks a stationary 0.2 kg soccer ball. The ball leaves her foot at a speed of 20 m/s.
    1. What impulse was delivered to the ball?
    2. The ball and Julieta’s foot experience equal-but-opposite forces, each 40 N strong. How long (in seconds) were the ball and foot in contact? Read the text aloud Show
  1. Marco strikes a punching bag with 80 N of force for 0.05 s. Marcela strikes a body bag with 60 N of force for 0.1 s. Who delivers a greater amount of impulse? Read the text aloud Show
  1. A ball with a mass of 200 g is thrown straight down at the floor. It strikes the floor at a speed of 10.0 m/s and bounces straight up again with a speed of 6.0 m/s. What is the change in the ball’s momentum? Read the text aloud Show
  1. A 1,200 kg car is heading due north at 14.0 m/s. It collides with an identical car heading due south at 14.0 m/s. What is the combined momentum of the cars before the collision? Read the text aloud Show
  1. Which of the following has greatest inertia? Which has greatest momentum?
    1. 6,000 kg elephant charging at 11 m/s
    2. 200 g bullet fired at 300 m/s
    3. 18,000 kg fire engine parked on the street Read the text aloud Show
  1. Sean, whose mass is 60 kg, is riding on a 5.0 kg sled initially traveling at 8.0 m/s. He brakes the sled with a constant force, bringing it to a stop in 4.0 s. What force does he apply? Read the text aloud Show
  1. A 1000 kg car is traveling north on a highway at 20 m/s. What is the car’s momentum when observed by another car traveling in the opposite direction at 20 m/s? Show

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