Momentum and Collisions - Mission MC2 Detailed Help

A 2.0-kg object moving at 5 m/s encounters a 30-Newton resistive force over a duration of 0.10 seconds. The final momentum of this object is approximately ____ kg•m/s.

(Note: Numbers are randomized numbers and likely different from the numbers listed here.)

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As is often the case, an effective strategy is critical to success on a physics question. An effective strategy for this question would be as follows:
  • Determine the impulse encountered by the object (see Formula Frenzy section).
  • Determine the momentum change of the object (see Minds On Time section).
  • Determine the pre-collision momentum of the object (see Formula Frenzy section).
  • Since the force is a resistive force, it takes momentum away from the object during the collision. Subtracting the momentum change from the pre-collision momentum of the object will result in the post-collision momentum of the object.

In a collision, an object changes its momentum; that is, it speeds up, slows down, and/or changes its direction. This momentum change is caused by and is equal to the impulse that it experiences. If the impulse is known (or if it can be calculated from force and time), then the momentum change is known. Knowing the momentum change allows one to determine the post-collision momentum value from knowledge of the pre-collision momentum value.

The momentum (p) of an object can be calculated from knowledge of its mass (m) and velocity (v) using the formula:   
p = m • v

The impulse encountered by an object can be calculated from the force (F) that is exerted on it and the time (t) over which the force is exerted. The formula is

Impulse = F • t


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