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. One of them would cause the specified change of state. This is one of the three versions:

Version 1
Pre- and post-collision information is shown. Identify the collision parameters that are consistent with the indicated change in momentum. (A + sign indicates a rightward direction; a - sign indicates a leftward direction.)


 
a.  ∆p = +40 kg•m/s
b.  ∆p = +8 kg•m/s
c.  Impulse =  +16 N•s
d.  F = +12 N, ∆t = 4 s
e.  F = +60 N, ∆t= 3.0 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.
 
The answer options include five choices. The choices are two momentum change values, one impulse value, and two combinations of force-∆time values. You will need to pick the answer using the principle that impulse is equal to momentum change. The momentum change value that you have just calculated should be equal to one of the five options. For the two answer options that include force-∆time values, you will need to calculate the impulse values. Do this by mulitplying F•∆t.  Once you have done this work, you can match an answer option to the calculated momentum change.
 

Try the links below to our Tutorial for more information:

Momentum

Impulse-Momentum Change Theorem

 


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