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

Collision and impulse

[SOLVED] collision and impulse

1. Homework Statement
A 1.0 kg ball drops vertically onto a floor, hitting with a speed of 20 m/s. It rebounds with an initial speed of 5 m/s.
(a) What impulse acts on the ball during the contact?
kg·m/s

(b) If the ball is in contact with the floor for 0.020 s, what is the average force exerted on the floor?
N



2. Homework Equations
p=m*v
deltap=J
F=m(deltav)/deltat


3. The Attempt at a Solution

For (a) i used p=m*v and deltap=J

so I got (1*-20)-(1*5)=-25

and for (b) i used that F=(m*deltav)/deltat

which came out to be... 1(-25)/.020=0.5 N

both answers were wrong and I'm not sure what is wrong with the formulas I used...

Any help is appreciated! Thanks!
 

Answers and Replies

536
2
25/0.020=1250
 
454
0
For a) the impulse is P_after - P_before and not P_before - P_after.

For b) see The reply of Mikelepore. I think you need to add the force of gravity as well.
 

Related Threads for: Collision and impulse

  • Last Post
Replies
6
Views
5K
  • Last Post
Replies
6
Views
933
  • Last Post
Replies
9
Views
8K
  • Last Post
Replies
24
Views
2K
  • Last Post
Replies
3
Views
2K
  • Last Post
Replies
2
Views
2K
  • Last Post
Replies
3
Views
808
  • Last Post
Replies
1
Views
889
Top