Can You Solve This Physics Problem on Kinetic and Potential Energy? (2024)

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In summary: I'll go ahead and give the summary for this conversation:In summary, the conversation discusses a physics problem involving an inclined plane and two masses. The summary covers the incorrect attempts at solving the problem and the correct solution for part (c). It also touches on the relationship between potential and kinetic energy in a lossless system and how it relates to the total energy over time. The conversation ends with a hint for solving parts (d) and (e) of the problem.

  • #1

riseofphoenix

295
2

Can You Solve This Physics Problem on Kinetic and Potential Energy? (1)

c, d, and e I don't know how to solve

For d I tried doing

vf2 = vi2 +2ad
Vf = √(2*9.8*2.3) = 6.71 m/s

Assuming the inclined plane is frictionless
Since m2 is roped to m1, it's velocity up the ramp will be 6.71m/s too

The total increase in KE is then 0.5[8+6]*6.71^2 = 315.16 J

^

"INCORRECT"

Right now I need a genius to tell me how to get the answer ASAP -.-

Since (d) is wrong, so is e. -.-
Story of my life.

  • #2

berkeman

Mentor

67,041
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riseofphoenix said:

Can You Solve This Physics Problem on Kinetic and Potential Energy? (2)

c, d, and e I don't know how to solve

For d I tried doing

vf2 = vi2 +2ad
Vf = √(2*9.8*2.3) = 6.71 m/s

Assuming the inclined plane is frictionless
Since m2 is roped to m1, it's velocity up the ramp will be 6.71m/s too

The total increase in KE is then 0.5[8+6]*6.71^2 = 315.16 J

^

"INCORRECT"

Right now I need a genius to tell me how to get the answer ASAP -.-

Since (d) is wrong, so is e. -.-
Story of my life.

For (c), how did you get that number? Isn't it just the sum of the two ΔU values?

  • #3

riseofphoenix

295
2

berkeman said:

For (c), how did you get that number? Isn't it just the sum of the two ΔU values?

m1 falls 2.3m and therefore has -6*9.8*2.3 = -135.24 J difference.

m2's PE increases 8*9.8*sin 30° = +39.2 J difference.

The total change then is 39.2 - 135.24 = -96.04 J

^ That was my previous answers, but I got that wrong too...
So I'm pretty much screwed.

  • #4

berkeman

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riseofphoenix said:

m1 falls 2.3m and therefore has -6*9.8*2.3 = -135.24 J difference.

m2's PE increases 8*9.8*sin 30° = +39.2 J difference.

The total change then is 39.2 - 135.24 = -96.04 J

^ That was my previous answers, but I got that wrong too...
So I'm pretty much screwed.

You left off the 2.3 for m2...

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  • #5

riseofphoenix

295
2

berkeman said:

You left off the 2.3 for m2...

(c)

m1 falls 2.3m and therefore has -6*9.8*2.3 = -135.24 J difference.

m2's PE increases 8*9.8*sin 30°*2.3 = +90.16 J difference.

The total change then is 90.16 - 135.24 = -45.08 J

Ok so how does this relate to part d and e though? How would I solve for those two last ones?

(d)

(e)

  • #6

berkeman

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riseofphoenix said:

(c)

m1 falls 2.3m and therefore has -6*9.8*2.3 = -135.24 J difference.

m2's PE increases 8*9.8*sin 30°*2.3 = +90.16 J difference.

The total change then is 90.16 - 135.24 = -45.08 J

Ok so how does this relate to part d and e though? How would I solve for those two last ones?

(d)

(e)

(d) asks for the change in KE. Since the system is frictionless...

  • #7

riseofphoenix

295
2

berkeman said:

(d) asks for the change in KE. Since the system is frictionless...

But I already tried solving for it and i got it wrong... (??)

  • #8

berkeman

Mentor

67,041
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riseofphoenix said:

But I already tried solving for it and i got it wrong... (??)

But you had the wrong answer for (c) before. Now you have that right.

What is the total energy of a system in terms of the potential and kinetic energies? If the system is lossless (no friction), what can you say about the total energy over time...?

See Also
An alpha particle q=+2e, m=4.00 u, travels in a circular path o... | Filo
  • #9

riseofphoenix

295
2

berkeman said:

But you had the wrong answer for (c) before. Now you have that right.

What is the total energy of a system in terms of the potential and kinetic energies? If the system is lossless (no friction), what can you say about the total energy over time...?

KEinitial + PEinitial = KEfinal + PEfinal
KEinitial + PEinitial = 0 + 0 (No friction)
KEinitial + PEinitial = 0?

  • #10

berkeman

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riseofphoenix said:

KEinitial + PEinitial = KEfinal + PEfinal
KEinitial + PEinitial = 0 + 0 (No friction)
KEinitial + PEinitial = 0?

Rearrange so you show the relationship between ΔKE and ΔPE...

  • #11

riseofphoenix

295
2

KE = -PE
KE = -mv?

  • #12

berkeman

Mentor

67,041
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riseofphoenix said:

KE = -PE
KE = -mv?

If you put Δs in front of your first equation, you would be on the right track...

  • #13

Perpendicular

49
0

Consider the total energy over time which is a constant. Hence change in PE must balance out change in KE. The rest is obvious.

  • #14

Perpendicular

49
0

As for (e) consider that you have a final change in KE, as well as the masses. You can now plug that into solve for velocity.

  • #15

berkeman

Mentor

67,041
19,864

Oops, Looks like riseofphoenix is on a temporary vacation from the PF for a different thread.

1. What is the difference between kinetic energy and potential energy?

Kinetic energy is the energy an object possesses due to its motion, while potential energy is the energy an object possesses due to its position or configuration.

2. How do you calculate the total mechanical energy of an object?

The total mechanical energy of an object is calculated by adding its kinetic energy and potential energy together. The formula is: E = KE + PE.

3. Can an object have both kinetic and potential energy at the same time?

Yes, an object can have both kinetic and potential energy at the same time. For example, a ball thrown into the air has both kinetic energy due to its motion and potential energy due to its height above the ground.

4. What factors affect the amount of kinetic and potential energy an object has?

The amount of kinetic and potential energy an object has is affected by its mass, velocity, and height. Objects with greater mass, higher velocity, and greater height have more kinetic and potential energy.

5. How can I increase my knowledge and understanding of kinetic and potential energy?

You can increase your knowledge and understanding of kinetic and potential energy by reading books and articles, watching educational videos, and conducting experiments related to these topics. You can also attend lectures or seminars on these subjects and ask questions to experts in the field. Practice solving problems involving kinetic and potential energy can also help improve your understanding.

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                      Can You Solve This Physics Problem on Kinetic and Potential Energy? (2024)

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