• Support PF! Buy your school textbooks, materials and every day products Here!

Collision and IMpulse

  • #1

Homework Statement


A 300g ball with a speed v of 6.0m/s strikes a wall at an angle theta of 30 degrees and then rebounds with the same speed and angle. It is in contact with the wall for 10ms. In unit-vector notation, what are (a) the impulse on the ball from the wall and (b) the average force on the wall from the ball?

http://ready2goxtr.googlepages.com/problem936.jpg


Homework Equations


Pi = Pf

Delta (P) = I
P = mv
<v being a vector>

Favg = I / (delta T)


The Attempt at a Solution



m = .3kg v = 6m/s theta = 30 degrees t = 10ms = .01s

a) Pi = PF

Pi = .3kg(Vcos(-30) i + Vsin(-30) j) = .26 kg * m/s i - 3 kg * m/s j

Pf = .3kg(Vcos(30) i + Vsin(30) j) = .26 kg * m/s i + 3 kg * m/s j

I = Delta (P) I = PF - PI

PF - PI = 6 kg * m/s j


b) I = sqrt(a^2 + b^2)
6kg * m/s / .01s = 600 N



I know i did it wrong. And thank you ahead of time.
 

Answers and Replies

  • #2
Doc Al
Mentor
44,872
1,120
Pi = .3kg(Vcos(-30) i + Vsin(-30) j) = .26 kg * m/s i - 3 kg * m/s j

Pf = .3kg(Vcos(30) i + Vsin(30) j) = .26 kg * m/s i + 3 kg * m/s j
Double check your arithmetic.
 
  • #3
whats wrong with it? Sorry if im a bit slow, all the chemotherapy i had last year sorta slowed me down i think.
 
  • #4
Doc Al
Mentor
44,872
1,120
  • #5
Oh Duh me. 0.9 but still, I highly doubt that I = 1.8 kg * m/s J
 
  • #6
well in that case I = 1.9 kg * m/s J and Favg = 180 N
 
  • #7
Okay so that must be right answer then?
 
  • #8
Doc Al
Mentor
44,872
1,120
Sounds good to me. Express your answers using unit vectors.
 
  • #9
Do i need to open up a new post for a new question?
 
  • #10
Doc Al
Mentor
44,872
1,120
Do i need to open up a new post for a new question?
In general: If it's a new problem, use a new thread. If it's a followup question on the same problem, ask it here.
 

Related Threads for: Collision and IMpulse

  • Last Post
Replies
6
Views
944
  • Last Post
Replies
6
Views
5K
  • Last Post
Replies
2
Views
3K
  • Last Post
Replies
3
Views
2K
  • Last Post
Replies
24
Views
2K
  • Last Post
Replies
3
Views
820
  • Last Post
Replies
2
Views
2K
  • Last Post
Replies
2
Views
3K
Top