What Are the Forces Acting on a Box Sliding Down a Ramp?

AI Thread Summary
A 115.0 kg box slides down a 25.0-degree ramp with an acceleration of 2.60 m/s², leading to calculations for the normal force, net force, and kinetic friction. The normal force is determined to be 1020 N, while the net force down the ramp is calculated at 299 N. Kinetic friction was initially estimated at 178 N but corrected to 179 N after reevaluating the calculations. The discussion emphasizes that when the coefficient of friction is unknown, kinetic friction can be found by subtracting the net force from the gravitational force acting on the box. Accuracy in calculations and significant figures is highlighted as crucial for physics assessments.
mizunopro
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A 115.0 kg box slides down a 25.0 degree ramp with an acceleration of 2.60 m/s squared. Find the normal force, the net force down the ramp, and the force of kinetic friction.

Gravity = 9.81 m/s2
Force of gravity = ma
Mew k = Force of Kinetic Friction/Normal Force

These are the parts that I've been able to find so far...
Normal Force= 1020N --> Force of gravity in the Y direction
The Net Force Down the Ramp= 299N --> 115kg x 2.60
Kinetic Friction = I have 178N and I got this by subtracting 299 from 478, but that was just a guess.

Any ideas?
 
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Some of the numbers are a little out from what I get, but it looks like you've used the correct method to get them all.

What are you stuck on, or did you just want confirmation?
 
i was just looking for some confirmation on the kinetic friction part of the problem. so, anytime a problem asks for kinetic friction and i don't have the mew value, i can just subtract the net force down the ramp from the force of gravity in the x direction? i think i realized that the calculation error was in 478-299..it should be 179 and not 178. thanks for your help..i have a test tomorrow and just wanted to make sure that i had this down.
 
mizunopro said:
i was just looking for some confirmation on the kinetic friction part of the problem. so, anytime a problem asks for kinetic friction and i don't have the mew value, i can just subtract the net force down the ramp from the force of gravity in the x direction? i think i realized that the calculation error was in 478-299..it should be 179 and not 178. thanks for your help..i have a test tomorrow and just wanted to make sure that i had this down.

Yes your methods look good, and if you don't have the coefficient of friction then yes you subtract the net force from whatever force is acting on the object to find the friction force. Do be careful with your numbers and significant figures though, as most people marking a physics test will penalise for that.
 
alright. once again, thank you for your help!
 

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