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Physics A: Problem Set 23: Impulse and momentum

recommended reading

High Marks: 1:117–1:121
Barron's Let's Review: 6.1–6.2 Newton's Second Law and Momentum
physics.info: Impulse & Momentum
Wikipedia: Impulse, Momentum
HyperPhysics: Impulse of force, Momentum
Khan Academy: Impacts and linear momentum
Mr. Machado: 06 Momentum, 10 Introduction to impulse, 11 Impulse - Solving for net force

definition of momentum

  1. Read the following excerpt of an interview with the American amateur naturalist Timothy Treadwell.

    Now, the bears I live with average, the males, eight to twelve hundred pounds [360 to 540 kg]. They're the largest bears in the world…. They've been clocked at 41 [mph] and they've run a hundred meter dash in 5.85 seconds, which a human on steroids doesn't even approach.

    Timothy Treadwell, 2001

    1. Compute the speed of a grizzly bear using Mr. Treadwell's hundred meter statement.
    2. Compute the momentum of a grizzly bear using the speed you calculated in part a. and the average mass stated by Mr. Treadwell.
    3. How fast would a 250 lb man have to run to have the same momentum you calculated in part b? (Do not use a calculator to compute your answer.)
    4. How fast would a 4000 lb car have to drive to have the same momentum you calculated in part b? (Do not use a calculator to compute your answer.)

impulse-momentum theorem

  1. A falling rubber ball of mass 0.025 kg strikes the ground traveling straight down at 4.0 m/s. Find the magnitude of the impulse that the ground gives to the ball if…
    1. the ground is soft and the ball stops dead
    2. the ground is hard and the ball bounces straight up at 2.0 m/s
  2. What is the basic idea behind crash safety features in cars like seatbelts, airbags, crumple zones, etc. What quantities in the impulse-momentum theorem (Ft = mv) change as a result of these features, how are they changed, and how does this result in increased safety during a crash?