OSColPhysl 5.1.019. [2153576] A contestant in a winter games event pushes a 43.0 kg block of ice across a frozen lake with a rope over his shoulder as shown in Figure 4.29(b). The coefficient of static friction is 0.1 and the coefficient of kinetic friction is 0.03. Fpull N Fpull Foully = pull SIn 25" Fpullx = Fpull eos 250 Ffriction Farau = m. q = ( 43 kg ) ( 9.8 m / s ! ) = 421.4 N Figure 4.29 In this case normal force is slightly Less than gravity because person (a) Calculate the minimum force F he must exert to get the block moving. is pulling upward on rock N [b) What is its acceleration once it starts to move, if that force is maintained? m/s a) vertical forces : Fgrav - N - Fondly = 0 ( no accel, vertically ) - ( 421.4 ) - N - Fpullsin 250 = 0 50 N = 421.4 - Fpull Sin 250 horizontal forces: Fpullx - Ffriction = D ( not accelerating yet ) Foul cos 25 - MN=O ( Fpull ) (0. 906) - (0. 1) (421.4 -(Foul1) (0.43)) = O b) horizontal forces : Fullx - Ffriction = ma Solve for N * kinetic friction ( 44 4 ) (605 25.) - (0.03 ) N = (43)(a) N : 421.4 - 44.4 5in 25" ( 44. 4 ) (105 25" ) - (0.03) (402.6) =(43 ) (a) = 402.6 N