Work/Conservation of Mechanical Energy

AI Thread Summary
To calculate the change in kinetic energy (KE) of an 80-N box being pulled up a 30-degree incline, the net force acting on the box must be determined. The applied force of 115 N and the gravitational force component along the incline (40 N) must be considered, along with the kinetic friction (coefficient of 0.22). A free body diagram is recommended to visualize the forces and calculate the net force responsible for the box's motion. The change in kinetic energy can be found by determining the initial and final kinetic energies, with the potential energy change also playing a role in the overall energy calculations. Understanding these concepts will clarify the problem-solving process for this scenario.
oceanscreams
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Homework Statement


An 80-N box is pulled 20m up a 30 degree incline by an applied force of 115 N that points upward, parallel to the incline. If the coefficient of kinetic friction between box and incline is 0.22, calculate the change in the kinetic energy of the box.

Homework Equations


ΔKE = 1/2mVf2-1/2mVi2 = mghi- mghf

The Attempt at a Solution


This is what i have understood so far, if there's a mistake please help me.

Given:
Fg= 80N so m=8.15kg
hi= 20m
θ= 30°
μk= 0.22
Fapp= 115N

I drew the ramp, and labeled all the forces. Also, I found Fgx to be 40N. My question is, what do they mean by change in KE? Should I find work done? If so, is it Wnet= Fdcosθ ? I'm really confused, I've spent more than an hour looking for solutions online, but I don't understand the explanation and I decided to try asking myself. Please explain what I should do, I've tried solving several times, but I can't seem to find the answer, and I also have a lot of other problems to solve.

Help is appreciated. Thank you
 
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What is the initial kinetic energy?
What is the final kinetic energy?
The difference is the change in kinetic energy.

Can you list all types of energy involved? Where does the box gain energy, where does it lose energy?
oceanscreams said:
Wnet= Fdcosθ ?
You did not introduce d. The formula can be relevant but I would choose a different approach.
 
oceanscreams said:
I drew the ramp, and labeled all the forces. Also, I found Fgx to be 40N. My question is, what do they mean by change in KE? Should I find work done? If so, is it Wnet= Fdcosθ ? I'm really confused, I've spent more than an hour looking for solutions online, but I don't understand the explanation and I decided to try asking myself. Please explain what I should do, I've tried solving several times, but I can't seem to find the answer, and I also have a lot of other problems to solve.

actually you should draw a free body diagram and find the net force which will be responsible for motion along the ramp-in up direction.then you can calculate the acceleration - one can assume initial kinetic energy to be zero and the potential energy change will be due to displacement along the ramp -
 
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