What are the methods for solving impulse and momentum problems?

[mikejones2000]

I am currently stuck on two problems:
#1 A bat hits a moving baseball. If the bat delivers a net eastward impulse of 0.9 N-s and the ball starts with an initial horizontal velocity of 3.8 m/s to the west and leaves with a 5.3 m/s velocity to the east, what is the mass of the ball (in grams)?

I set J=deltaP
.9=95.3+3.8)m
m=.9/(5.3+3.8).

#The second problem has a force vs. time for an impulsive force graph and asks: The force shown in the figure below is the net eastward force acting on a ball. The force starts rising at t=0.012 s, falls back to zero at t=0.062 s, and reaches a maximum force of 35 N at the peak. Determine with an error no bigger than 25% (high or low) the magnitude of the impulse (in N-s) delivered to the ball. Hint: Do not use J = FΔt. Look at the figure. Find the area of a nearly equally sized triangle.

I am sure tthis problem is very simple but do not have a confident approach for some reason, I presume I find the time when it peaks at 35 N(.062-.012) and use this as my base? Then I would apply A=.5(35)(.062-.012)?

Any help would be greatly appreciated.

 

[G01]

It seems like you methods are correct, is there a problem with you answers?

Also if this graph is the graph for the basball and bat in part one the area of your approximate triangle should be approximately .9Ns

 

[mikejones2000]

I got 0.0989 for the first problem, I am not sure if its in kilograms or grams and
0.875 for the second one. I know I got at least one problem out of the three assigned and presume it has to be one of these because the other is a multiple choice problem. Thanks in advance for any help.

 

[Kurdt]

If you're using SI units for your working it will be Kg.

With regards to question 1 remember that delta p is p_f - p_i. Also these are vector quantities but I think you've taken that into account just a reminder.

For question 2 if they say use a triangle then use a triangle it should be fine. The area under the curve would normally be determined by the integral of F(t) but since its not given the triangle method should give a fair approximation.