course Phy231
4/1/10 8:30am
A ball starting from rest rolls 9 cm down an incline on which its acceleration is 22 cm/s2, then onto a second incline 38 cm long on which its acceleration is 13 cm/s2. How much time does it spend on each incline?
1st incline a=22cm/s^2 'ds=9cm v0=0cm/s^2
vf=+-'sqrt(v0^2+2a'ds)=+-'sqrt(2a'ds)=+-'sqrt(2*22cm/s^2*9cm)=19.9cm/s
'dv=19.9cm/s-0cm/s=19.9cm/s 'dt='dv/a=19.9cm/s/22cm/s^2=.905s
2nd incline a=13cm/s^2 'ds=38cm v0=19.9cm/s
vf=+-'sqrt(v0^2+2a'ds)=+-'sqrt((19.9cm/s)^2+2*13cm/s^2*38cm)=+-'sqrt(1384.01)=37.202cm/s
'dv=37.202cm/s-19.9cm/s=17.302cm/s 'dt='dv/a=17.302cm/s/13cm/s^2=1.331s"
&#Very good responses. Let me know if you have questions. &#