Working out speed, kinetic energy and resistive force

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Homework Help Overview

The discussion revolves around calculating speed, kinetic energy, and resistive forces in a physics context. Participants are exploring the relationships between gravitational potential energy, kinetic energy, and work done by forces, particularly friction.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Problem interpretation, Assumption checking

Approaches and Questions Raised

  • Participants discuss the calculation of speed and its dependence on distance and time, questioning how to derive kinetic energy from mass and speed. There is also exploration of how to relate work done to kinetic energy and frictional forces.

Discussion Status

Some participants have provided guidance on solving initial parts of the problem, suggesting that resolving earlier questions may clarify subsequent ones. There is ongoing exploration of the relationship between work, force, and distance, particularly in the context of friction.

Contextual Notes

Participants express uncertainty regarding the application of equations and the nature of forces involved, particularly whether the frictional force is constant. There is a focus on understanding the implications of these assumptions in the context of the problem.

Meezus
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Homework Statement


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Homework Equations


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The Attempt at a Solution



a) I'm not sure how to calculate speed without having both distance and time but I believe it will revolve around calculating gravitational potential energy and kinetic energy.

bi) I think this is just simply using the formula kinetic energy = 1⁄2 × mass × speed2.

bii/biii) I'm really struggling to work out these. I think It might revolve around using the speed from the first question and then take it away from 22m/s.
 
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You are on the right track for a) and b.i).
I suggest you solve those two first. It might then be more apparent how to solve b.ii)
 
haruspex said:
You are on the right track for a) and b.i).
I suggest you solve those two first. It might then be more apparent how to solve b.ii)

I believe I have solved them now.
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if possible could you help with the last one?
 
Meezus said:
if possible could you help with the last one?
What equation do you know relating work and distance?
 
haruspex said:
What equation do you know relating work and distance?

Work = Force x Distance.?
 
Meezus said:
Work = Force x Distance.?
Looks promising. How would it apply here? Explain in words.
 
haruspex said:
Looks promising. How would it apply here? Explain in words.

is it something like:
Work done = change in kinetic energy,
Work = - 11250 J?
 
Meezus said:
is it something like:
Work done = change in kinetic energy,
Work = - 11250 J?
Yes, but I meant the work = force x distance equation. Can you express that in respect of frictional force and the circumstances in this question?
 
haruspex said:
Yes, but I meant the work = force x distance equation. Can you express that in respect of frictional force and the circumstances in this question?

The amount of work done is equal to the frictional force times by the distance? I'm sorry I'm not 100% sure.
 
  • #10
Meezus said:
The amount of work done is equal to the frictional force times by the distance? I'm sorry I'm not 100% sure.
Yes (given that the force is constant; in general the relationship is an integral).
 
  • #11
haruspex said:
Yes (given that the force is constant; in general the relationship is an integral).

Am I able to work out the magnitude from this?
 
  • #12
Meezus said:
Am I able to work out the magnitude from this?
Yes, you have all the information. (One clarification: the force is not constant as a vector here, but it is constant in magnitude. This works out ok because the force of friction is always parallel to the motion, so it still reduces to force x distance traveled along the path. You do not know and do not need to know the end-to-end displacement as a vector.)
 

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