Question

what is total KE of two pucks before collision

Answer 1

@Vincent-Lyon.Fr

Answer 2

Just add up the two KE of the pucks.

Answer 3

ok but when should i consider the x and y direction

Answer 4

KE is a scalar quantity, depending on speed, not on velocity. So no need here to bother with x's and y's.

Answer 5

okay so if i want to find the momentum then it is

Answer 6

1/2 mv^2

Answer 7

MV is momentum

Answer 8

Momentum is a vector quantity depending on velocity. So x's and y's have to be considered properly.

Answer 9

okay but if they ask te magnitude of total momentum of the 2 pucks system after collision

Answer 10

the answer is 5J i did not get

Answer 11

the KE is 5J because it is scalar but why the total momentum 5J

Answer 12

Start again with KE and forget momentum right now. 5J is the right answer.

Answer 13

yes

Answer 14

now they are asking total momentum of the pucks

Answer 15

after collision

Answer 16

what will be the kinetic energy after collision ??

Answer 17

Value of total momentum is 5 kg.m/s, it is not 5 J. (different units)

Answer 18

Total momentum before collision = total momentum after collision
(always true)

Answer 19

ya i know that but we dont know whether it is elastic or inelastic

Answer 20

for KE to be conserved

Answer 21

Hold on!

Can you ask/answer questions one at a time? It's totally confusing.

Answer 22

LOL:)

Answer 23

alright consider the same diagram (2) what is teh total momentum of two puck system after collision

Answer 24

Well, it's the same as BEFORE the collision, so what you have to do is work out total momentum before collision.

Answer 25

got you thx for replying

Answer 26

Since the two momentum vectors are at right angles, their sum can be found using the Pythagorean theorem; the direction can be found using SOH CAH TOA (specifically, the tangent function)

Answer 27

http://www.physicsclassroom.com/mmedia/momentum/2di.cfm
this may help you LOL