PLEAAASSEEE HELLPPP MEEEEEEEEEEEE

Calculate the force of friction for a 5kg aluminum block being pulled with constant velocity (uniform motion), up a steel plank that is at a 30 degree angle to the horizontal.

Question

PLEAAASSEEE HELLPPP MEEEEEEEEEEEE

Calculate the force of friction for a 5kg aluminum block being pulled with constant velocity (uniform motion), up a steel plank that is at a 30 degree angle to the horizontal.

anonymous · Answer

friction equals the mass times gravity times the cosine of the angle.
let friction equal y.
y = (5Kg)(9.8m/s^2)(cos(30))

anonymous · Answer

so it is 7.6 ?

agent0smith · Answer

The friction force also involves the coefficient of friction, 
$$F _{f} = \mu _{k} mg \cos \theta $$

But we aren't given the coefficient of kinetic friction mu

anonymous · Answer

oo so shouldnt it be the coefficient of friction for the aluminum to steel which would be .47 ? and then the answer would be  .355 right?

agent0smith · Answer

Is your calculator in radians? 5x9.8xcos30x0.47 shouldn't equal 0.355.

anonymous · Answer

whoops it was is it 19.94 ?

agent0smith · Answer

Yep.

agent0smith · Answer

don't forget units, newtons, N.

anonymous · Answer

Thankyou soo much! and right labels:) haha

agent0smith · Answer

No prob :)

anonymous · Answer

sorry i missed the aluminum and steel part...