Elastic Collision and final speed

  • Thread starter learnin'
  • Start date
  • #1
2
0

Homework Statement



a) Initially, mass one (2.40 kg) has a velocity of 5.70 m/s and mass two (2.20 kg) is at rest. After they collide, mass one emerges at an angle theta = 31.0 degrees. What is the speed of mass one after the collision if the collision is completely elastic? (Note, there are actually two possible answers two this problem, choose the solution which has m1 going as fast as possible.)

b) What is the angle phi, between mass two's velocity and the initial velocity of mass one? (Give your answer as a positive number in degrees.)

c)What is the final speed of mass two after the collision?

m1= 2.40kg
v1i= 5.70m/s
m2 = 2.2kg
theta1= 30 deg
v1f= ??
theta 2 = ??
v2f = ??

Homework Equations



Because it's elastic,

mechanical energy is conserved.
1/2 m1(v1i)^2 = 1/2m1(v1f)^2 + 1/2m2(v2f)^2

Momentum is conserved
for x direction: m1v1i= m1v1f cos(theta1) + m2v2f(theta2)
for y direction: m1v1i= m1v1f sin(theta1) + m2v2f(theta2) = 0

tan (theta2) = (v1f* sin (theta1))/(v1i - v1f * cos (theta1))

The Attempt at a Solution



In all honesty, I'm a little thrown off because I don't know what v1f is.
 

Answers and Replies

  • #2
2
0
I tried dividing the xdirection equation with ydirection equation and then getting 1 = tan (theta1) + tan(theta2)....but it didn't work... I need help... or a little guidance.
 

Related Threads on Elastic Collision and final speed

Replies
3
Views
4K
Replies
16
Views
3K
  • Last Post
Replies
1
Views
827
Replies
1
Views
1K
Replies
11
Views
15K
  • Last Post
Replies
3
Views
10K
Replies
1
Views
3K
Replies
3
Views
11K
  • Last Post
Replies
5
Views
7K
Replies
2
Views
9K
Top