Solve Force and Impulse Homework: Speed of Tennis Ball After Collision

[huybinhs]

Homework Statement

The Figure shows an approximate representation of the contact force versus time during the collision of a 36-g tennis ball with a wall. The initial velocity of the ball is 151.6 m/s perpendicular to the wall. What is the speed of the tennis ball after the collision?

Homework Equations

P = mv

The Attempt at a Solution

I did find 3 Area in the pic the add them up. I got 10200 total, then what's next?
Any help would be appreciated! ;)

 

[thrill3rnit3]

P₀ + J = P_f

 

[huybinhs]

P(0) = (36/1000) * 151.6 = 5.4576 N*m

Pf = (36/1000) * vf with Pf = total of 3 Areas, correct?

 

[thrill3rnit3]

P(0) = (36/1000) * 151.6 = 5.4576 N*m

Pf = (36/1000) * vf with Pf = total of 3 Areas, correct?

No, in the equation I told you, J represents the area of the figure. Do you see why?

 

[huybinhs]

so P(0) = (36/1000) * 151.6 = 5.4576 N*m

then 5.4576 + 10200 = (36/1000) vf => vf = 2.83 * 10^5 m/s, right?

 

[thrill3rnit3]

so P(0) = (36/1000) * 151.6 = 5.4576 N*m

then 5.4576 + 10200 = (36/1000) vf => vf = 2.83 * 10^5 m/s, right?

Time in the graph is given in milliseconds (ms).

 

[huybinhs]

If so 10200 will be = 10.2

=> 5.4576 + 10.2 = (36/1000) vf => vf = 435 m/s Wrong! Why?

 

[thrill3rnit3]

If so 10200 will be = 10.2

=> 5.4576 + 10.2 = (36/1000) vf => vf = 435 m/s Wrong! Why?

Does the force act on the same direction as the motion?

 

[huybinhs]

so u mean J in this case is just = 9 ?

 

[thrill3rnit3]

so u mean J in this case is just = 9 ?

I mean it's negative, and where did you get 9?

 

[huybinhs]

so I got the 1st area = 0.5 * 0.002 * 1200 = 1.2

2nd = 0.007 * 1200 = 8.4

3rd = 0.001 * 0.5 * 1200 = 0.6

so now why should i do? please be more specific!

 

[thrill3rnit3]

so I got the 1st area = 0.5 * 0.002 * 1200 = 1.2

2nd = 0.007 * 1200 = 8.4

3rd = 0.001 * 0.5 * 1200 = 0.6

so now why should i do? please be more specific!

add the 3 = 10.2

I'm saying that since the force of the wall is acting opposite of the motion, then maybe the impulse should be negative (-10.2)

 

[huybinhs]

Got it! Thanks for your patience ;)

 

[thrill3rnit3]

Got it! Thanks for your patience ;)

You're most welcome