Block, Ramp, Friction, and Spring

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Homework Help Overview

The discussion revolves around a physics problem involving a block being pulled up an incline, friction, and a spring. The problem includes calculating work done, speed upon reaching a horizontal surface, spring constant, and rebound distance on the incline.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Problem interpretation

Approaches and Questions Raised

  • Participants discuss using energy conservation versus force analysis to approach the problem. Questions arise about the application of conservation of energy and the correctness of equations used for calculations.

Discussion Status

Some participants have made attempts to apply conservation of energy and have shared their results, while others are questioning the validity of their equations and seeking clarification on the principles involved. There is an ongoing exploration of different methods and interpretations without a clear consensus.

Contextual Notes

Participants are navigating through the problem with various assumptions about energy states and forces acting on the block, including the effects of friction and the spring's behavior. There is mention of specific values and conditions that may influence the calculations.

r34racer01
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A man pulls a block of mass m = 19 kg up an incline at a slow constant velocity for a distance of d = 6 m. The incline makes an angle q = 32° with the horizontal. The coefficient of kinetic friction between the block and the inclined plane is µk = 0.2.

a) What is the work Wm done by the man?
I got Wm =782.31

At the top of the incline, the string breaks and the block, assumed to be at rest when the string breaks, slides down a distance d = 6 m before it reaches a frictionless horizontal surface. A spring is mounted horizontally on the frictionless surface with one end attached to a wall. The block hits the spring, compresses it a distance L = 0.4 m, then rebounds back from the spring, retraces its path along the horizontal surface, and climbs up the incline.

b) What is the speed v of the block when it first reaches the horizontal surface?

c) What is the spring constant k of the spring?

d) How far up the incline d1 does the block rebound?


 
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You can attempt this question in one of two ways: energy conservation or forces analysis.
 
Hootenanny said:
You can attempt this question in one of two ways: energy conservation or forces analysis.

Ok, well which do you recommend?
 
r34racer01 said:
Ok, well which do you recommend?
Personally, I always find conservation of energy the most straight forward.
 
Ok well some recommended I try v = sqrt 2(gh- ug cos 33), but that didn't work so now I'm lost again. How should I apply conservation of energy here?
 
r34racer01 said:
How should I apply conservation of energy here?
What does the principle of conservation of energy (COE) state? Can you use COE to write down an equation for part (b)?
 
Ok so using COE I was able to figure out the the Wg+Wf = KE at the bottom and setting that equal to .5mv^2 I got v = 6.51.

Now I'm trying to solve for K when the spring is compressed. I know that at this point all the energy is in the spring so I thought KE = -k(x2^2 - x1^2)/2. So I did 403.04 = - k(0.6^2)/2 but that didn't work. Anyone know what I did wrong?
 
r34racer01 said:
Ok so using COE I was able to figure out the the Wg+Wf = KE at the bottom and setting that equal to .5mv^2 I got v = 6.51.
Are you sure about that equation? How much energy does the block have at the top of the incline?
 

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