12. A 10-kg box is dragged across the floor by a rope which makes a 30-deg angle to the horizontal (see D force? illustration). The tension in the rope is 40 N, and the coefficient of kinetic friction between the box and the floor is / = 0.10. If the box slides 10 m across the floor, what was the work done on the box by the frictional in = 10 k A) 20 J B) - 40 J 0 J 0: 30 D ) * = 10 M - 80 J E) - 100 J ..10 dag 13. An electric scooter has a motor capable of delivering 750 W of power. The scooter specs say that the scooter itself is 29 kg, and a typical rider is 68 kg. A rider encounters a steep uphill, and the sign says it is a 10% grade (which is an incline angle of 5.7 degrees). How fast can the rider drive this scooter up this hill? P= 750 W A) 2 m/s B) 3 m/s M , : 29 ky C) 5 m/s MR: 68 kg D) 8 m/s E) 10 m/s 0 = 5.7 14. A 13.0 kg load of bricks hangs from one end of a rope that passes over a small, frictionless pulley. A 31.0 kg counterweight is suspended from the other end of the rope as it is shown in the figure. The system is released from rest. What is the magnitude of the upward acceleration of the load of bricks? A) 4.01 m/s2 M = 13 kg B) 8.06 m/s2 C) 12.91 m/s2 T - myy = my 4 D) 15.03 m/s2 E) 17.82 m/s2 1 29 - T = m 24 131 leg g ( mz - my ) = a (my +mz ) 9 : 9.8 (31- 13) (23 + 37 ) m T - m 13 leg - 98 ( 14 ) 5 of 6