A 5-kg crate is resting on a horizontal plank. The coeï¬ƒ-

cient of static friction is 0.5 and the coeï¬ƒcient of kinetic
friction is 0.4. After one end of the plank is raised so
the plank makes an angle of 25
�with the horizontal, the
force of friction is?

3 answers

Wc = m*g = 5kg * 9.8N/kg = 49 N, = Wt.
of crate.

Fp = 49*sin25 = 20.3 = Force parallel to
ramp.
Fv = 49*cos25 = 44.4 N. = Force perpendicular to ramp.

Fs = u*Fv = 0.5*44.4 = 22,2 N. = Force
of static friction.

BOOOTY HOLE

oten