The coefficient of static friction between a 40kg crate and concrete surface is 0.25. Find the magnitude of the minimum force needed to keep the crate stationary on the concrete base inclined at 45o to the horizontal. [G = 10ms-1]

kaelindaureaus380

3 months ago

FORCE REQUIRED TO KEEP A BODY ON A PLANE
F =mgsinØ - umgcosØ
F=mg(sinØ-ucosØ)
F = 40 x 10(sin45° - 0.25cos45°)
sin 45° and cos 45° = 0.707

F = 400 ( 0.707 - 0.25 x 0.707)
F = 400( 0.707 - 0.177)
F = 400 x 0.53
F= 212N
OPTION C IS LEGIT

Boluwa124456

1 year ago

U=F/R
R=mgcoso(tita)
0.25= F/0.25*40*10*cos45
F= 70.71
w= mgsin0(tita)
w= 40*10sin45
w= 282.8
W-F = 282.8-70.71
= 212N

s.samuel

3 years ago

Someone should please explain thank you

jedroy

2 months ago

Here's the technical explanation if the crate was stationary then the force tending to take it down the slope will counteract it's friction but here we're asked the force to keep it stationary that means the crate is moving down the slope meaning force tending to take it down is now more than the frictional force.
To make it stable you have to solve for a force that if added to friction will stop it from moving
The force tending to take it down the slope is mgsin∅ but this force is not same with friction since it is not stationary
the frictional force will be solved for using the coefficient of friction and normal reaction
if gotten we'll realize that
mgsin∅ = 282.8 while Fr= 70.71
we now see why there's a discrepancy and why the crate is moving it's because the force moving it along the slope is more than the friction.
To keep it stationary we add a force to the friction to counteract this force that'll be 282.8-70.71 this should give the additional force to be added getting 212N

Refhord

3 years ago

Does Momentum force means total force?

banitoobi

7 years ago

The solved and is 287.3

Emzyuniques7

2 years ago

the answer it correct but answer it no d same in calculator when i calculate how dey got the answer