• Momentum is a vector describing how difficult it is to stop a moving object

  • Total momentum is the sum of individual momenta

  • C:\25225E85\B09A51C6-0574-4A0C-A2C1-496768C10C63_files\image118.png

  • Units are kg·m/s or N·s

Example 1: Changing Momentum

  • An Aichi D3A bomber mass (3600 kg) departs from its aircraft carrier with a velocity of 85 m/s due east. What is its momentum?


  • After it drops its payload, its new mass is 3000 kg and it attains a cruising speed of 120 m/s . What is its new momentum?



  • As you observed in the previous problem, momentum can change

  • A change in momentum is known as an impulse (J)

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Example 2: Impulse

  • The D3A bomber, which had a momentum of 3.6e5 kg·m/s, comes to halt on the ground. What impulse is applied?


Relationship Between Force and Impulse

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Example 3: Force from Momentum

  • The momentum of an object as a function of time is given by p=kt2, where k is a constant. What is the equation for the force causing this motion?


Impulse-Momentum Theorem


Example 4: Impulse-Momentum

  • A 6-kg block, sliding to the east across a horizontal, frictionless surface with a momentum of 30 kg·m/s, strikes an obstacle. The obstacle exerts an impulse of 10 N·s to the west on the block. Find the speed of the block after the collision.

    -ιο».9+ 30 Ι) e.osE

Example 5: Water Gun

  • A girl with a water gun shoots a stream of water than ejects 0.2 kg of water per second horizontally at a speed of 10 m/s. What horizontal force must the girl apply on the gun in order to hold it in position?


Impulse from F-t Graphs

  • Impulse is the area under a Force-time graph

  • Impulse is equivalent to a change in momentum

    Force Impulse

Example 6: Impulse from Force

  • A force F(t)=t3</sup is applied to a 10 kg mass. What is the total impulse applied to the object between 1 and 3 seconds?


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