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course Phy 231
2-19-11 about 11:00am
A ball starting from rest rolls 11 cm down an incline on which its acceleration is 29 cm/s2, then onto a second incline 32 cm long on which its acceleration is 14 cm/s2. How much time does it spend on each incline?ds(1st incline)= 11cm
a( 1st incline)= 29cm/s^2
v0= 0
vf(1st incline)= sqrt (0 + 2(29cm/s^2)(11cm))= 25.26cm/s
dt(1st incline)= vAve/ds= ((25.26cm/s+0)/2)/11cm= 1.15s
ds(2nd)= 32cm
a(2nd)= 14cm/s^2
v0(2nd)= 25.26cm/s
vf(2nd)= sqrt( (25.26cm/s)^2 + 2(14cm/s^2)(32cm))= 39.17cm/s
dt(2nd)= ((25.26cm/s + 39.17cm/s)/2)/32cm= 1.01s
&#This looks good. See my notes. Let me know if you have any questions. &#