Ball collides with a door and pushes it open

Thread starter TjGrinnell
Start date May 13, 2020
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SUMMARY

The discussion centers on the application of the conservation of mechanical energy equation, represented as KEb1 + PEb = KEb2 + PEb. Participants emphasize the necessity of not assuming conservation of mechanical energy without sufficient justification. Alternative laws, such as the principles of momentum conservation, are suggested for analyzing the collision of a ball with a door, highlighting the importance of context in applying these physical laws.

PREREQUISITES

Understanding of kinetic energy (KE) and potential energy (PE) concepts
Familiarity with the conservation laws in physics
Knowledge of momentum conservation principles
Basic grasp of collision dynamics

NEXT STEPS

Research the principles of momentum conservation in collisions
Study the conditions under which mechanical energy is conserved
Explore the differences between elastic and inelastic collisions
Learn about energy loss mechanisms in real-world collisions

USEFUL FOR

Students of physics, educators teaching mechanics, and engineers involved in collision analysis will benefit from this discussion.

May 13, 2020

TjGrinnell

Homework Statement: A door has a mass of 9.00 kg, a height of 2.00 m, a width of 1.00 m, and a moment of inertia of 3.00 kg*m2 about its axis. It is initially at rest and partly open. A 2.00 kg ball is thrown at the door. When it hits the door it is 1.20 m above the floor and 0.450 m from the hinge axis. It is moving at 3.50 m/s perpendicular to the door's surface, and it bounces back, also perpendicular to the door's surface at 2.00 m/s.
What is the angular speed of the door after the collision
If the collision takes place over 0.05 s, what was the average force between the ball and the door?

Relevant Equations: KE[SUB]b1[/SUB]+PE[SUB]d[/SUB]=KE[SUB]b2[/SUB]+KE[SUB]d[/SUB]

F[SUB]avg[/SUB]=m(v[SUB]f[/SUB]-v[SUB]0[/SUB])/t
Have to type here because of picture. I think I may have done this wrong the first time and I wanted to know if i should use the conservation equation as shown above, or I the one in my work correct?
And also is the second formula the correct one in order to get the average force?
Thank you