Peter M. answered • 11/14/23
Tutor
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(288)
AP Physics 1 & 2, IB Physics. Engineer with 30 years teaching Physics
vf2 = vi2 + 2ad
solve for a
a = Δv / Δt
solve for Δt
P = ΔKE / t = 1/2 m (Δv)2 / t
Ff = μ FN = μ mg.
W = Ff ⋅ d
W = ΔKE = 1/2 m (Δv)2 = μ mg d
solve for μ
Benson A.
Continuing on for part a, after calculating the acceleration value, this could be used alongside the acceleration equation you gave and the final and initial velocities given in problem. Using all of these I obtained a value of about 0.704 seconds for the amount of time taken for the box to slow. Is t = 0.704 seconds correct?
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11/23/23
Benson A.
For part b, using the equation you gave, along with the information given by problem, I obtained a power value of about 17.76 watts. Therefore for part b is P = 17.76 W correct?
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11/23/23
Benson A.
For part c, using the equation you gave, along with the info given by problem, I got a coefficient of friction value of 0.134. Is this correct?
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11/23/23
Peter M.
tutor
Benson, thank you for your comments.
I am going to be a little cagey in my response.
One can determine if an answer is correct by using sound Problem Solving Methodology (PSM). That means:
1) Draw a picture of the situation presented.
Visual representations lend form to words.
Engage both sides of your brain.
2) Write down the data with symbols and units.
Include what you are solving for.
3) Write down the appropriate formulas that include both the knowns and the unknowns.
4) Rearrange formulas to solve for the unknowns.
THIS IS AN IMPORTANT STEP. For three reasons:
i) To establish the relationships between the variables for the situation.
That way you can interrogate the relationships to see if they make sense.
ii) You should only move the data (with units) once, rather than playing a shell game. This eliminates a source of error and also makes including units less arduous.
iii) You can do a unit analysis of calculations to verify the veracity of your algebra operations.
5) Input data with units and solve (see step 4)
6) Do the answers make sense?
In reviewing your answers, the acceleration value makes sense as it is near the value of g.
The time and Power results are also reasonable.
a coefficient of friction that is less than 1 also makes sense.
If you have executed valid PSM, there is no need for an answer key.
It also has a few benefits:
- Someone can audit your work and use their fresh eyes to identify any errors.
- When someone asks you how to solve the problem, rather than explaining each step, you can save time by just having them review your work.
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11/23/23
Benson A.
Hello thank you for responding, and providing advice. I really appreciate that. Anyway, for part a you instruct first to find the acceleration value. I do that based on the kinematic equation you provided, along with the information given by the problem. I got an acceleration value of about a = -7.105 m/s^2. Is this value for the acceleration correct?11/23/23