Question

Polly Ester and Ray Ahn are doing the Elastic Collision lab on a low-friction track. Cart A has a mass of 1.00 kg and is moving rightward at 27.6 cm/s prior to the collision with Cart B. Cart B has a mass of 0.50 kg and is moving leftward with a speed of 42.9 cm/s. After the magnetic repulsion of the two carts, Cart A is moving leftward at 10.1 cm/s. Determine the post-collision speed and direction of cart B.

I don't get how to exactly solve this...i'm getting 2/3 of it, just need to know how to do the last equation/formula.

Answer 1

try showing a bit of you work, maybe just the general steps.

Answer 2

p1=m1v1
p1=(1.00kg)(27.6cm/s)
p1=10.1kg*cm/s

p2=m2v2
p2=(0.50kg)(42.9cm/s)
p2=21.45kg*cm/s

I don't know from there.

Answer 3

Polyester and Rayon., really? Why don't you conserve energy and check?

Answer 4

What do you mean conserve energy? This is the conservation of momentum...

Answer 5

magnetic repulsion implies that now b attains momentum of a and a attains momentum of b and both start moving in opposite direction
so now P1=21.45 and P2=10.1
now divide P2 by its mass so as to calculate speed of b in opposite direction. . .

Answer 6

That gives me 20.2m/s and 21.45m/s..correct?

Answer 7

20.5 is direction b and is toward right. . .

Answer 8

but the correct answer is 32.5 cm/s right.

http://www.physicsclassroom.com/calcpad/momentum/problems.cfm

number 26.

Answer 9

ohk then there is a twist in the story i missed this line. . .
" After the magnetic repulsion of the two carts, Cart A is moving leftward at 10.1 cm/s. "
i have to make some changes now

Answer 10

@some1
p1=m1v1
p1=(1.00kg)(27.6cm/s)= 27.6
"p1=10.1kg*cm/s" <----- wrong

p2=m2v2
p2=(0.50kg)(42.9cm/s)
p2=21.45kg*cm/s

I don't know from there.

Answer 11

Really sorry....I didnt read the question properly the first time.
you have \[p _{Ai} + p _{Bi} = p_{Af} + p_{Bf}\]
i: Initial; f: final

And you know the values of pAi, pBi and pAf. pBf can subsequently be found.

Answer 12

hm. i think i'll try that. thanks aish and theyatin. :D