P = F delta T!

  1. okay Im not sure what the right answer is out of these multiple choices because Im not sure how exactly to use F delta T.

    A 4.0-N force acts for 3.0 sec on an object. The force suddenly increases to 15 N and acts for one more second. What impulse was imparted by these forces to the object?

    a. 12 Ns
    b. 15 Ns
    c. 16 Ns
    d. 27 Ns

    I got like...both A and B as possible answers but im not sure which one is right..I used F delta T to get 12 because I just did 4 x 3. Then I got 15 by doing 15 x 1. Im not sure how to use the change in time... when i played around with it i was getting numbers that were not any of the choices. Any help is much appreciated.
     
  2. jcsd
  3. StatusX

    StatusX 2,567
    Homework Helper

    Impulse is additive. That is, if you have an impulse of A over one period of time, and an impulse of B over another period, then the total impulse over both periods is A+B. (taking into account the direction each time)
     
  4. Thanks! Let's hope I do good on this re-test after I bombed the first momentum test. haha
     
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