Homework Help: phisics

Posted by greg on Sunday, October 28, 2012 at 12:47am.

The drawing shows two boxes resting on frictionless ramps. One box is relatively light and sits on a steep ramp. The other box is heavier and rests on a ramp that is less steep. The boxes are released from rest at A and allowed to slide down the ramps. The two boxes have masses of 12 and 38 kg. If A and B are 5.5 and 1.5 m, respectively, above the ground, determine the speed of (a) the lighter box and (b) the heavier box when each reaches B. (c) What is the ratio of the kinetic energy of the heavier box to that of the lighter box at B?

phisics - Elena, Sunday, October 28, 2012 at 5:00am
(a)
ΔKE=ΔPE
KE(B)-KE( A)=PE(A)-PE(B)
mv²/2 -0 =mgh(A)-mgh(B)
v=sqrt{2g[h(A)-h(B)]}

(b) KE1/KE2 = {m1•gh(A)-mgh(B)}/ {m2•gh(A)-mgh(B)} =
=m1/m2

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