Answer Happy

6) As shown, we assume that the lower arm has a mass of 2.8 kg and its center of gravity (i.e. where you would draw its weight vector) is 12 cm from the elbow-joint pivot. How much force must the extensor muscle in the upper arm exert on the lower arm to hold a 7.5 kg ball at rest? (C) 750 N (A) 100 N (D) 1000 N (B) 500 N (E) 1500 N 7) The two point masses shown are connected by a very light stick which may be rotated about either the x-axis or y-axis. What is the moment of inertia of this set of masses about the x-axis? (A) 1.9 x 10-2kgm² (C) 1.2 x 10-² kgm² (E) 7.0 x 10² kgm² (B) 7.0 x 10³ kgm² (D) 1.9 x 10³ kgm² 8) A boy of mass m and a girl of mass 2m are both initially at rest at the center of a frozen pond. They push each other so that she slides to the left at speed v across the frictionless ice and he slides to the right as shown. What is the magnitude of the boy's velocity the moment after the two push each other? (A) 플러 (B) V (C) v 2m 2.5 cm 0.2 kg 0.1 kg (D) V 30.0 cm- Elbow joint 0.3 m 0.1 m (E) 2v