Simple Collisions Question Solution | Conservation of Momentum

[hasnain721]

[SOLVED] simple collisions question

Homework Statement

http://img180.imageshack.us/img180/1253/28157442gm4.jpg

Homework Equations

√(2gh)

The Attempt at a Solution

a)


Gravitational potential energy = kinetic energy

this gives u

√(2gh)

= 0.815 metres


b)
i)
In a closed system, total momentum is always conserved.

ii)

Momentum before = momentum after


momentum before :
mass X velocity
(80/100) kg X 4 m/s = 0.32kgm/s

momentum after :
mass X velocity
((80/100) X 3) kg X x = 0.32 kgm/s

therefore x = 1.33 m/s

Is that rite?


and for c) :

ah i get it now!

 

[Kurdt]

All is fine up to the momentum calculations where you use (80/100) as the mass. This should be (80/1000) or (8/100). You seem to have the right value for the momentum though so that's probably just a typo. What did you get for part c?

EDIT: Just noticed you've solved it.

 

[hasnain721]

All is fine up to the momentum calculations where you use (80/100) as the mass. This should be (80/1000) or (8/100). What did you get for part c?

oh yes srry! for part c i got : 2.67 seconds is tht rite?

 

[Kurdt]

oh yes srry! for part c i got : 2.67 seconds is tht rite?

Looks fine to me.

 

[hasnain721]

Looks fine to me.

cheers!