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Dynamics ID Free Response File

11 Comments

Daniel Angotti • 1 year, 7 months agologin to reply

Would it be possible to get the worked-out solutions to these problems? Thanks

John Ennis • 1 year, 7 months agologin to reply

Daniel, at this time, we don't make them all available, but will send individual ones as you request. John

Katherine Boutin • 1 year, 2 months agologin to reply

For question 2. When finding the acceleration of block m1 relative to the horizontal surface (m2), I got a1 =(F-mum1g)/m1 which is given in the answer key. For part C, why do we have to subtract the accelerations to find the acceleration relative to block m2? Isn't that what we found in part B? Thank you!

John Ennis • 1 year, 2 months agologin to reply

Katherine, that would be the acceleration relative to the ground. Since the bottom block is also moving to the right, the relative acceleration between the two blocks requires the subtraction. The bottom block is "running away" from the top block, so it takes longer for the top block to slide off the end. John

Sabrina Vargas • 1 year, 2 months agologin to reply

Would I be able to have the worked out solution for problems 3,6, and 7. Thank you.

John Ennis • 1 year, 2 months agologin to reply

Sabrina, Here are problems 3 and 7. I'll get #6 to you tomorrow. John

John Ennis • 1 year, 2 months agologin to reply

Sabrina, Here are problems 3 and 7. I'll get #6 to you tomorrow. John

Katherine Boutin • 1 year, 2 months agologin to reply

Thank you John. I fell into the trap of not reading the question completely.

John Ennis • 1 year, 2 months agologin to reply

We all fall into that trap! John

Michael Chin • 3 weeks, 2 days agologin to reply

I believe that the answer to question 7, part c is wrong. The answer to question 7, part B should also include the alternative option where friction is also equal to tension. f = (Mass of block C) x g. The problem with question 7, part c is that the solutions state that (static friction between A and B) EQUALS (static coefficient between B and A) x (Weight of block B). That is the same error that many students make. it is (LESS THAN OR EQUAL TO). Instead, (static friction between A and B) EQUALS (mass of B) x (acceleration). That changes the final calculation to: 𝑎=[𝑀_𝐶 − 𝜇_𝑘𝐴 (𝑀_𝐴+𝑀_𝐵 )]𝑔/(M_A+M_B+M_C )

John Ennis • 3 weeks agologin to reply

Michael, Thank you so much for your correction. We have updated the problem set on the website. John

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