During a collision, an object experiences an impulse that changes its momentum. The impulse is equal to the momentum change. The impulse is the product of Force•∆Time. The momentum change is the product of Mass•∆Velocity. One can use the Force•∆Time = Mass•∆Velocity relationship to determine the set of collision parameters required to change the object's momentum from the initial state value to the final state value.
 

There are three very similar versions of this question. Each version provides a before-after diagram showing the initial and final momentum of an object. Five sets of collision parameters are presented. Two of them, when combined, would cause the specified change of state. This is one of the three versions:

Version 1
For the given pre- and post-collision information, identify the collision parameters that are consistent with the indicated momentum change. Pick two sets of parameters. (A + sign indicates a rightward direction; a - sign indicates a leftward direction.)


a.  Impulse = +8 N•s
b.  Impulse = -8 N•s
c.  F = +4 N, ∆t = 2 s
d.  ∆p =  +24 kg•m/s
e.  F = + 32 N, ∆t = 0.5 s
 

The diagram in this question shows an object mass (in kg) and a pre-collision and a post-collision velocity value. The velocity values can be used to calculate a velocity change (∆v). You can calculate velocity change by subtracting the initial value from the final value. The momentum change can be calculated by multiplying mass by ∆velocity. You will need to calculate this momentum change (∆p) before you can answer the question.
 
This question includes two different "impulses" or collisions. So you will need to pick two answers that when combined (added together) provide the momentum change you just calculated. The principle that should guide your answer selection is that the momentum change is equal to the total or combined impulse.
 
Of the five answer options, two include impulse values, one is a momentum change value, and the final two are both combinations of force-∆time values. We recommend that you first calculate the impulse values from the provided force-∆time values. You would be wise to write down the values you calcuate. Once done, inspect the five answer options and use a trial and error method to find two options which add together to give the momentum change that you have calculated. 
 

Try the links below to our Tutorial for more information:

Momentum

Impulse-Momentum Change Theorem

 


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