A block of mass is positioned on a right-triangular ramp of vertical height and mass . A spring with force constant and natural length is attached between the ramp and the wall as shown. All surfaces are smooth. The block can slide along the ramp surface, and the ramp can slide along the floor. The ramp makes an angle with respect to the horizontal. There is a downward gravitational acceleration .
At time , the block is at the top of the ramp, and the spring is at its natural length . Both the block and the ramp are initially at rest. The block slides down the ramp over time.
The block reaches the floor at time . Let be the minimum spring length over the period of time between and . Enter your answer as the following quantity:
Details and Assumptions:
Here, "m" can mean "meter", or it can refer to the block mass, depending on the context
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denotes the
floor function
- During the period of interest, the block remains fully in contact with the ramp, and the ramp remains fully in contact with the floor.
- The block's size is negligible
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Whoa! We’re finally finished. But for those of you (initially including me) who thought this problem is easy and does not need these steps, I finally
present to you a WRONG solution which oversimplifies things, and since the spring is quite stiff and motion is short, leads to the RIGHT answer.
This would probably make you appreciate the rigour of the correct solution.
Please feel free to ask any doubts in comments. Hope this helps.