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Lesson: Impulse and Collisions

Define the impulse of a force as the product of the force applied and the time interval over which the force is applied. Demonstrate that impulse applied to an object is equivalent to the object's change in momentum.

Worksheet: Impulse and Collisions • 3 Questions

Q1:

Water from a fire hose is directed horizontally against a wall at a rate of 50.0 kg/s and a speed of 42.0 m/s. Calculate the force exerted on the wall, assuming the water’s horizontal momentum is reduced to zero.

  • A N
  • B N
  • C N
  • D N
  • E N

Q2:

A 65.0-kg-mass person jumps from the first floor window of a burning building and lands almost vertically on the ground with a horizontal velocity of 3.00 m/s and vertical velocity of m/s. Upon impact with the ground he is brought to rest in a short time. The force experienced by his feet depends on whether he keeps his knees stiff or bends them.

Find the magnitude of the impulse on the person from the impact on the ground.

Find the direction from the horizontal of the impulse on the person from the impact on the ground.

Find the average horizontal force on the person’s feet if the person keeps his legs stiff and straight and his center of mass drops by only 1.00 cm vertically and 1.00 cm horizontally during the impact.

  • A N
  • B N
  • C N
  • D N
  • E N

Find the average vertical force on the person’s feet if the person keeps his legs stiff and straight and his center of mass drops by only 1.00 cm vertically and 1.00 cm horizontally during the impact.

  • A N
  • B N
  • C N
  • D N
  • E N

Find the average horizontal force on the person’s feet if the person bends his legs throughout the impact so that his center of mass drops by 50.0 cm vertically and 5.00 cm horizontally during the impact.

Find the average vertical force on the person's feet if the person bends his legs throughout the impact so that his center of mass drops by 50.0 cm vertically and 5.00 cm horizontally during the impact.

Q3:

A car crashes into a large tree that does not move. The car decelerates from a velocity of 30 m/s to rest over a distance of 1.3 m. A driver of mass 70 kg is sitting in the car when it crashes.

What impulse is applied to the driver by the seatbelt, assuming he follows the same motion as the car?

  • A kg⋅m/s
  • B kg⋅m/s
  • C kg⋅m/s
  • D kg⋅m/s
  • E kg⋅m/s

What is the average force applied to the driver by the seatbelt?

  • A N
  • B N
  • C N
  • D N
  • E N
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