Question

questions 4 and 5 please

4. A 1.50 kg point mass is 200.0 cm from a 3.00 kg point mass. Where is their center of mass, measured from the 1.50 kg mass? Xcm =- 5. Starting from rest, a disk spins with a constant angular acceleration. After 2 minutes it has completed 50 revolutions. How many revolutions will it have completed at 4 minutes? a) 25 rev b) 71 rev. c) 100 rev d) 200 rev

Answer 1

4)

suppose 1.5 kg is sitting at ( 0, 0) and 3 kg is sitting at ( 200 , 0 ) so

X_com = ( 1.5 *0 + 3*200 )/ (3+1.5) =133.333333 cm

so COM is 133.33 cm away from 1.5 kg mass

5)

θ = ωi*t +1/2*α*t^2

50 *2pi =0 +0.5*α*120^2

α = 50 *2pi /( 0.5*120^2) =0.0436332313 rad/s²

speed at 120 sec

v = u +at = 0 + 0.0436332313*120 = 5.23598776 rad/s

θ = ωi*t +1/2*α*t^2

θ = 5.23598776*120 + 1/2*0.0436332313*120^2 =

= 942.47779656 rad

no. of revolution =942.47779656/(2pi) = 150

so total revolution = 200