71. We may treat all 25 cars as a single object of mass m= 25 ×5.0 ×104kg and (when the speed is 30 km/h = 8.3 m/s) subject to a friction force equal tof= 25 ×250 ×8.3 = 5.2 ×104N. (a) Along the level track, this object experiences a “forward” force Texerted by the locomotive, so that Newton’s second law leads to 4655.2 10(1.25 10 )(0.20) 3.0 10 NTfmaT−=¡=×+×=×.(b) The free-body diagram is shown next, with
This is the end of the preview. Sign up
access the rest of the document.
This note was uploaded on 05/17/2011 for the course PHY 2049 taught by Professor Any during the Spring '08 term at University of Florida.