# Question 3 Quiz Week 9

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Question 3 Quiz Week 9

I don't have the correct answers for this/any quiz.

A basketball of mass m dropped from a certain height hits the ground with a downward speed v(1) and bounces back with an upward speed v(2) leaving the ground. Ignoreair resistance during the process. What is the impulse applied by the ground to the metal ground.

I don't want the answer, but rather to correct my method of solving (if my answer is wrong) because this is what I'll have during the exam.

Delta(P)=Impulse

mv(2)-mv(1)=I    But here I pick the downward direction to be +ve; therfore v(2) is actually -v(2)

-m(v2+v1)=I and since downward is postive; Impulse is upward and m(v1+v2) option d

Correct or wrong?
asked Oct 27, 2013

If you pick downward as positive, then $v_2$ is negative and $v_1$ is positive. So your $\Delta P$ would be negative too -- a negative P2 minus a positive P1 gives a total negative $\Delta P$, which means an upward $\Delta P$. In this case, d is correct.