Perfectly elastic collisoin with missing variables

Watch
PatchworkTeapot
Badges: 10
Rep:
?
#1
Report Thread starter 5 years ago
#1
Two balls labelled A and B have masses mA=1.0kg and mB=1.5kg. Initial velocities vAi=2.0m/s and vBi=-1.0m/s. If they collide in a perfetly elastic collision, what is vAf (the final speed of ball A) after the collision?

What I know so far is
Momentum is conserved, kinetic energy is conserved.

P1=0.5 kg m/s P1=P2
Ek1=2.75J Ek1=Ek2

P2= (mA x vAf) + (mB x vBf) Ek2= (0.5mA x vAf^2) + (0.5mB x vBf^2)

How do you solve this equation without knowing the final velocity of ball B? You have to relate the equation for momentum with the equation for kinetic energy, but I don't know how to do that without knowing the velocity of B.
0
reply
Smithenator5000
Badges: 9
Rep:
?
#2
Report 5 years ago
#2
(Original post by PatchworkTeapot)
Two balls labelled A and B have masses mA=1.0kg and mB=1.5kg. Initial velocities vAi=2.0m/s and vBi=-1.0m/s. If they collide in a perfetly elastic collision, what is vAf (the final speed of ball A) after the collision?

What I know so far is
Momentum is conserved, kinetic energy is conserved.

P1=0.5 kg m/s P1=P2
Ek1=2.75J Ek1=Ek2

P2= (mA x vAf) + (mB x vBf) Ek2= (0.5mA x vAf^2) + (0.5mB x vBf^2)

How do you solve this equation without knowing the final velocity of ball B? You have to relate the equation for momentum with the equation for kinetic energy, but I don't know how to do that without knowing the velocity of B.
Hey there,

Try forming two separate equations: one using the conservation of momentum and one using the conservation of kinetic energy. As these equations will both involve two unknowns (the final velocity of A and B), you should be able to solve the equations simultaneously. I hope that this has been helpful.
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

Feeling behind at school/college? What is the best thing your teachers could to help you catch up?

Extra compulsory independent learning activities (eg, homework tasks) (11)
7.33%
Run extra compulsory lessons or workshops (25)
16.67%
Focus on making the normal lesson time with them as high quality as possible (25)
16.67%
Focus on making the normal learning resources as high quality/accessible as possible (21)
14%
Provide extra optional activities, lessons and/or workshops (42)
28%
Assess students, decide who needs extra support and focus on these students (26)
17.33%

Watched Threads

View All