Solve Physics 101 Practice Exam 2 Problem 21: Total Kinetic Energy

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The discussion revolves around solving a physics problem related to total kinetic energy and mechanical energy conservation. Participants calculated the total kinetic energy of a system and discussed the implications of gravitational potential energy changes, emphasizing that work done by gravity can be positive or negative depending on the direction of force and displacement. Clarifications were sought regarding the correct application of formulas for work and torque, with specific attention to the use of sine and cosine in torque calculations. The conversation also touched on momentum conservation in collision problems, highlighting the importance of vector components in determining final velocities. Overall, the thread illustrates the complexities of applying physics concepts to problem-solving in a practice exam context.
  • #51
Okay, Last 2 i promise, http://online.physics.uiuc.edu/cgi/courses/shell/phys101/spring06/prep2a.pl?practice/exam3/sp05 Okay so i drew a free body diagram and i have Friction froce - Tension = Ia ?? Right or am i missing somethin cause i am not getting the asnwer. and http://online.physics.uiuc.edu/cgi/courses/shell/phys101/spring06/prep2a.pl?practice/exam3/fa03 6. I tried doing everything, anyhint i also drew free body diagram.
 
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  • #52
Alt+F4 said:
Okay, Last 2 i promise, http://online.physics.uiuc.edu/cgi/courses/shell/phys101/spring06/prep2a.pl?practice/exam3/sp05 Okay so i drew a free body diagram and i have Friction froce - Tension = Ia ?? Right or am i missing somethin cause i am not getting the asnwer.
I assume you're talking about problem 4. Don't confuse force with torque. Hints: What is \alpha? (Key: rolling without slipping.) What force produces the torque about the center of mass?

and http://online.physics.uiuc.edu/cgi/courses/shell/phys101/spring06/prep2a.pl?practice/exam3/fa03 6. I tried doing everything, anyhint i also drew free body diagram.
One way to solve this is to use conservation of energy. Hint: Realize that the cylinder will have both rotational and translational KE. (The two are related, since it rolls without slipping.)
 
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  • #53
k thanks alot, i just took my physics exam and Aced it i got an A, :smile: thanks for all ur help
 
  • #54
Awesome! That's what I like to hear.
 

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