# phsyics

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A brick of mass 1.5 kg slides down an icy roof inclined at 30.0° with respect to the horizontal.

(a) If the brick starts from rest, how fast is it moving when it reaches the edge of the roof 1.75 m away? Ignore friction.
m/s ?

(b) Redo part (a) if the coefficient of kinetic friction is 0.09.
m/s ?

• phsyics -

Wb = mg = 1.5kg * 9.8N/kg = 14.7 N. =
Wt. of brick.

Fb = 14.7N. @ 30 Deg.=Force of brick. Fp = 14.7*sin30 = 7.35 N. = Force parallel to roof.
Fv = 14.7*cos30 = 12.7 N. = Force perpendicular to roof.

a. h = 1.75*sin30 = 0.875 m.
Vf^2 = Vo^2 + 2g*h.
Vf^2 = 0 + 19.8*0.875 = 17.15.
Vf = 4.14 m/s. = Final velocity.

b. Same as (a).

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