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Find magnitude of friction force

Hi everyone,

Not looking for a specific question to be answered here! Just a bit confused. If asked to find the magnitude of the frictional force and magnitude of the normal reaction for a particle on an incline plane...what do you do? I found a value for Fr and a value for R and the friction coefficient. But i dont understand what it means by finding the magnitude? Any tips?

Thank you!

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Reply 1

aesir22

Just to add the particle is in equilibrium

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Reply 2

willp93

Original post by aesir22

Just to add the particle is in equilibrium

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ok fairly difficult to explain without diagrams etc but i'll give it a go.
if the particle is in eqbm then the forces pulling it down the slope are equal to those pulling it back up, and the friction is always in the opposite direction to that in which the particle is moving. draw a diagram with all the forces on to make it simple. normally only gravity is acting against friction (unless an external force is applied) so friction would be equal to the gravity component that is in line with the slope (i.e. it equals mg*sin(x), where x is the angle of the slope). hope this makes sense :smile:

Reply 3

aesir22

Thanks! So i worked out the friction force and it equals the same as the grav force. The reaction force is larger. I'll take a pic lol ImageUploadedByStudent Room1394297340.315795.jpg

ImageUploadedByStudent Room1394297340.315795.jpg

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Reply 4

willp93

Original post by aesir22

Thanks! So i worked out the friction force and it equals the same as the grav force. The reaction force is larger. I'll take a pic lol ImageUploadedByStudent Room1394297340.315795.jpg

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your equations are fine, so assuming your working is ok too then yes! :P
i always found it easier to write the equation as forces in one direction = the forces in the other, rather than 1 minus the other = zero, less likely to make a silly error with the signs :biggrin: