Impulse of a ball hitting the wall

In summary, the pool ball rebounds at an equal and opposite angle of 45 degrees. The impulse was 10.8166 N, and the change in momentum is q - p = (c-a,d-b).

Homework Statement

Calculate the change in momentum of a 120g pool ball hitting at 9m/s and rebounding at 6m/s. It rebounds at an equal and opposite angle of 45 degrees.

Pi = 9m/s
Pf = 6m/s
angle = 45 degrees

The Attempt at a Solution

I have done all my calcs in the picture below which shows a diagram

I have concluded that the impluse was 10.8166 N, somehow I don't think I have done this right

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I have concluded that the impluse was 10.8166 N, somehow I don't think I have done this right
Well, you're right that you're wrong. Given that the impulse $I = m\Delta v$, consider breaking the velocities into orthagonal components. Which component will the normal force change?

welcome to pf!

hi miniradman! welcome to pf!
I have done all my calcs in the picture below which shows a diagram

I have concluded that the impluse was 10.8166 N, somehow I don't think I have done this right

looks fine , except that you've not yet multiplied by the mass

(and do you need to specify the direction of the https://www.physicsforums.com/library.php?do=view_item&itemid=340" also?)

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tiny-tim said:
hi miniradman! welcome to pf!

looks fine , except that you've not yet multiplied by the mass

(and do you need to specify the direction of the https://www.physicsforums.com/library.php?do=view_item&itemid=340" also?)
I don't think so...

Also, I have trouble remembering which one to flip around and make a negative? Is there are certain rule of guideline I have to follow to do this?

Thanks ;)

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I have trouble remembering which one to flip around and make a negative? Is there are certain rule of guideline I have to follow to do this?

i'm not sure i follow

if the momentum before is p = (a,b), and the momentum after is q = (c,d),

then the change in momentum is q - p = (c-a,d-b)

What I did, was I flipped the 6m/s around so it becomes -6m/s (beause I took them way like vectors). Because it is on an angle of 45 degrees, I added the vectors head to tail

is this right?

yes, you can either subtract the original vectors, tail-to-tail, or flip one so that it becomes adding, which is head-to-tail

awesome! Thanks mate ;)

1. What is the impulse of a ball hitting the wall?

The impulse of a ball hitting the wall is the change in momentum that occurs when the ball collides with the wall. It is a vector quantity, meaning it has both magnitude and direction.

2. How is the impulse of a ball hitting the wall calculated?

The impulse of a ball hitting the wall is calculated by multiplying the force of the impact by the time it takes for the impact to occur. This can be represented by the equation Impulse = Force x Time.

3. How does the mass of the ball affect the impulse?

The mass of the ball does not directly affect the impulse, but it does affect the magnitude of the force of impact. A heavier ball will have a greater force of impact, resulting in a larger impulse.

4. Can the impulse of a ball hitting the wall be negative?

Yes, the impulse of a ball hitting the wall can be negative if the direction of the force of impact is opposite to the initial direction of motion of the ball. This could occur if the ball is rebounding off the wall in the opposite direction.

5. How does the elasticity of the ball and wall affect the impulse?

The elasticity of the ball and wall can affect the impulse by influencing the force of impact and the amount of time it takes for the impact to occur. A more elastic ball and wall will result in a longer impact time and a smaller force of impact, leading to a smaller impulse.

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