Very difficult Hockey stick puck problem. Please help

  • Thread starter Thread starter madman143
  • Start date Start date
AI Thread Summary
The discussion revolves around a physics problem involving a hockey stick and puck collision. The key points include determining the final speed of the combined center of mass after an inelastic collision, calculating the distance from the collision point to the center of mass, and analyzing angular momentum before and after the collision. Participants emphasize using the formula for completely inelastic collisions to derive the final velocity and discuss the conservation of linear and angular momentum. The challenge lies in expressing the answers in terms of the given variables without specific numerical values.
madman143
Messages
11
Reaction score
0

Homework Statement



Please help. Have no clue?
A hockey stick of mass m_s and length L is at rest on the ice (which is assumed to be frictionless). A puck with mass m_p hits the stick a distance D from the middle of the stick. Before the collision, the puck was moving with speed v_0 (note: a v with subscript zero) in a direction perpendicular to the stick, as indicated in the figure. The collision is completely inelastic, and the puck remains attached to the stick after the collision.

Homework Equations


i suppose v_f=v_0+m_p/m_s+m_p
but it gives a wrong answer.
As for the others, i have no clue. please help..


The Attempt at a Solution

 
Physics news on Phys.org
All you've done is told us a story about a hockey puck. What is the question?

(Unless I'm blind)

:smile:
 
thats why i called myself madman, innit.
anyway, here are the question, if anyone can have a go at them, id be greatful..
1.Find the speed v_f of the centre of mass of the stick+puck combination after the collision.
Express v_f in terms of some of the following quantities: v_0, m_p, m_s, and L.
2.After the collision, the stick and puck will rotate about their combined centre of mass. How far is this centre of mass from the point at which the puck struck? In the figure, this distance is (D-b).
3. What is the angular momentum L_cm of the system before the collision, with respect to the centre of mass of the final system?
Express L_cm in terms of the given variables (do not use b).
4. What is the angular velocity omega of the stick+puck combination after the collision? Assume that the stick is uniform and has a moment of inertia I_0 about its centre. Your answer for omega should not contain the variable b
5. Which of the following statements are TRUE?

1) Kinetic energy is conserved.
2) Linear momentum is conserved.
3) Angular momentum of the stick+puck is conserved about the centre of mass of the combined system.
4) Angular momentum of the stick+puck is conserved about the (stationary) point where the collision occurs.
i told you it was tough.
 
It looks like since you arn't give any actual values in the question, you can only answer the question in terms of the variables given.

Try using the formula for completely inelastic collisions.

M1v1+m2v2 = (m1 + m2) V'
OR (mass 1)(initial velocity of mass 1) + (mass 2)(initial velocity of mass 2) = (Mass 1 + mass 2)(Final velocity of both masses as one)

Just try plugging in what you're given.
 
We had this question on the Mastering Physics online assignment thing last week ;-)
 
Thats why I wan't to see an attempt at a solution first.
 
Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
Back
Top